In the Name of Allaah, the Most Merciful, the Bestower of Mercy
All praise is for Allaah, Lord of the universe. And may His peace and blessings be upon the foremost of those who fear Allaah and the seal of the prophets (Muhammad), as well as his family, his companions and (all) those who follow them in righteousness, until the Day of Recompense.
As for what follows, then:
These are some brief, yet comprehensive words concerning the difference between advising and condemning, for indeed they are counterparts in the sense that they both consist of mentioning something about a people that they hate to have mentioned. However, the distinction between the two is something that is not understood by many people. Thus, Allaah is the One who grants correctness.
Know that mentioning something about a person that he hates to have mentioned (about him) is forbidden, if the objective behind that is for nothing else but to dispraise and declare (his) faults and defects. 
However, if there is found in this mentioning, a beneficial good for the general masses of Muslims – specifically for some of them – and the objective behind it is to accomplish this beneficial good, then it is not forbidden, but rather recommended.
The scholars of Hadeeth have agreed with this (principle) in their books on the subject of Al-Jarh wat-Ta'deel,  and they have mentioned that there is a difference between criticizing hadeeth reporters and backbiting them. And they further refuted those who placed these two (categories) at the same level, such as those constantly engulfed in worship (all the time) as well as others who do not possess sufficient knowledge. 
Furthermore, there is no difference between 1) criticizing narrators of one of the hadeeth scholars (huffaadh) and distinguishing whose reports are to be accepted from them and whose reports are not, and between 2) clarifying the mistake of one who has erred with regard to understanding the meanings of the Book and the Sunnah, interpreted some aspect of it incorrectly, and who has adhered to something false. This (clarifying) was done so that this individual would not be followed in that which he erred in. The scholars have also unanimously agreed upon the permissibility of doing this (clarification). 
This is why we find that the books they authored concerning the various sciences of the religion - such as tafseer, explanation of hadeeth, Fiqh, the difference of opinions amongst the scholars, and so on - are filled with arguments  and refutations of the statements of those who voiced weak opinions from the scholars of the past and present, such as the Sahaabah, the Taabi'een and those after them.
Not one of the people of knowledge abandoned (doing) this (clarification). Nor would he claim in his (refutation) to disparage, dispraise or defame the individual whose saying he was refuting, unless the author (he was refuting) was from those whose speech consisted of wickedness and who displayed vile manners when expressing himself. In this circumstance, his wickedness and vileness were forsaken apart from the original state of refuting and opposing him. And this (refutation) was based upon sound arguments and stable proofs. The reason for all this was due to the unanimous agreement of the scholars of this Religion that the truth which Allaah sent His Messenger, (صلى الله علیه وسلم), with must be made known, and so that all of the Religion can be purely for Allaah (alone) and so that His word can be the highest.
Furthermore, all of them acknowledge that grasping the entirety of the knowledge, without neglecting any part of it, is not a level that has been reached by any of them, nor has anyone from the scholars of the past or those of the present claimed to have reached it. For this reason, the Imaams of the Salaf – those whose knowledge and merits are widely and unanimously agreed upon – used to accept the truth from anyone that disclosed it to them, even if that person was young.  And they would advise their companions and followers to accept the truth, even if it appeared in someone else's statements.
An example of this is found in 'Umar's, (رضي الله عنه), saying when he stated his opinion concerning the dowry of women. A woman responded to him by reciting Allaah's statement:
"But if you intend to replace a wife with another, and you have given one of them a qintaar (large amount of gold in dowry), take not the least bit of it back." 
Upon this, 'Umar went back on his opinion and said:
"A woman has spoken correctly and a man has erred." 
And it has also been reported that he said:
"Everyone is more understanding of Fiqh than 'Umar." 
Some of the famous (scholars) used to say, upon having formed an opinion concerning a matter:
"This is the opinion that we have derived, so anyone that brings an opinion better than it, we shall accept it (from him)."
Imaam Ash-Shaafi'ee used to go to great extents with regard to this understanding, for he would advise his companions to follow the truth and accept the Sunnah, even if it should appear to them in contradiction to their (own) opinions. And he encouraged them to, at that point, throw his opinion against the wall (i.e. throw it away).  He would say in his books :
"There is no doubt that you will find in them (my opinions) that which contradicts the Book and the Sunnah, for Allaah, the Most High, says:"And if it (the Qur'aan) were from someone other than Allaah, they would have found many contradictions in it."  "
And what is more profound than this is his saying:
"No one ever debated me except that I noticed: either the truth was manifested on his tongue or on my tongue."
This indicates that his intention was for nothing else but to manifest the truth, even if it were found on the tongue of someone other than him, such as those who debated or differed with him.
Whoever possesses this type of condition, then indeed he will not hate having his opinion rejected, nor having his contradiction of the Sunnah clarified, whether during his lifetime or after his death.
This was the way the scholars of Islaam from past and present – those who are the protectors of it and who rise to support it – used to think about others. They would also not detest the opposition they received from those that contradicted them with a proof that was made known to them. This was even if the proof that these individuals (who opposed them) used was not strong according to them, such that they would accept it and abandon their proof in place of it.
This is why Imaam Ahmad (رحمه الله) would mention Ishaaq Ibn Raahawaih (رحمه الله) while praising and commending him. And he would say:
“Even if he does contradict (me with regard to the Sunnah) in some matters, then indeed, the people will never cease to differ with one another.”
Or it is as he said.
And many times he (رحمه الله) was presented with the words of Ishaaq and other Imaams, and their sources from where they derived their opinions, and he would not agree with them in their opinion, nor would he reject their views or their evidences for it, even though he would not agree with any of that. 
Imaam Ahmad (رحمه الله) approved of what was related from Haatim Al-Asam, when it was said to him:
“You are a non-Arab and do not speak eloquently, yet no one debates you, except that you silence him. So with what do you gain victory over your opponents?”
So he responded:
“By three things: I become happy when my opponent speaks correctly (on a point). I become grieved when he errs. And I withhold my tongue from him, lest I should say something that would harm him”
- or something with this meaning - so Ahmad (رحمه الله) said:
“How wise of a man he is.”
Therefore, refuting weak (erroneous) opinions and clarifying the truth with regard to what opposes it, based upon sound evidences, is not from what these scholars detested. Rather, it was from that which they loved and for which they commended and praised those who did it.
So it does not enter into the realm of backbiting at all. But suppose there is someone that hates to have his error, which contradicts the Sunnah, exposed. In this case, there is no consideration given to his hatred for that, because hating to manifest the truth - if it is in opposition to the opinion of a man - is not from those matters that are praiseworthy.
Rather it is an obligation on the Muslim to love that the truth be made manifest and that the Muslims (in general) are aware of it, regardless of whether it is in conformity or in opposition to his (personal) view. 
This is from the aspects of sincerity (naseehah) towards "Allaah, His Book, His Messenger, His Religion, the leaders of the Muslims and their common folk." And this is, in fact, the Religion itself, as the Prophet, (صلى الله علیه وسلم), has informed us. 
As for clarifying the mistake of one of the scholars who erred in the past, then if one observes good manners in his speech and does well in his refutation and response, then there is no harm upon him nor is there any blame that he can be accused of. And if it turns out, that he was misled by this (past) scholar's (erroneous) opinion, then there is (also) no harm (i.e. sin) on him.
When a statement would reach some of the Salaf that they rejected, they would say:
"This person has not spoken the truth."
This example is taken from the saying of the Prophet, (صلى الله علیه وسلم):
"'Abu As-Sanaabil has not spoken the truth." 
when news reached him, (صلى الله علیه وسلم), that he issued a ruling that a woman whose husband passed away, while she was pregnant, was not permitted to remarry upon delivering her child, but instead had to wait until four months and ten days had passed. 
The righteous Imaams went to great lengths in forsaking the weak sayings (opinions) of some of the scholars. And they refuted them with the highest degree of refutation, as Imaam Ahmad (رحمه الله) used to censure Abu Thawr and others in their opinions that they were alone in saying. And he went to great extremes in refuting them in these opinions.
All of this relates to the outer and apparent matters. As for the inner affairs, then if one's intention in doing that (criticism) is to just clarify the truth and so that the people will not be deceived by the sayings of someone who erred in his opinions, then there is no doubt that this individual will be rewarded for his intention. And by doing this with this intention, he falls into the category of being from those who show sincerity to Allaah, His Messenger, the leaders of the Muslims and their common folk. And it is the same whether the one who clarifies the mistake is young or old. So he has a good example in those scholars who refuted the (weak) opinions of Ibn ‘Abbaas, (رضي الله عنه)maa, which have been declared irregular, and which have been rejected by the scholars, such as (his opinion) regarding mut'ah (temporary divorce), sarf (bartering), 'umratain and other than that. 
And he has a good example in those who refuted the opinion of Sa’eed Ibn Al-Musayyib (رحمه الله) concerning his allowing the woman that was divorced three times (to remarry her first husband) with just the (marriage) contract,  and his other opinions that contradicted the established Sunnah. And there are the scholars who refuted Al-Hasan Al-Basree with regard to his opinion that a wife should not mourn for her deceased husband, and who refuted 'Ataa for his (weak) opinions, and Taawoos in the numerous issues in which he differed from the scholars, as well as all those (other scholars) whom the Muslims have agreed upon their guidance, knowledge, respect and reverence.
And not one of the scholars considered those that didn't agree with him in these issues and their likes to be belittling or defaming these Imaams.
The books of the Muslim scholars from past and present, such as the books of Ash-Shaafi'ee, Ishaaq, Abu 'Ubaid, Abu Thawr and those scholars of Hadeeth and Fiqh that came after them, are filled with the clarifications of these opinions. And if we were to mention that in words, this discussion would be severely prolonged.
But if the intention of the one refuting is to expose the faults of the one being refuted and to debase him and manifest his ignorance and shortness of knowledge, then this is forbidden, whether the refutation is done in the presence of the one being refuted or in his absence, or whether it is done during that person's lifetime or after his death. This type of action falls under the acts which Allaah condemns in His Book and which He threatens the one who does it, concerning his slander and backbiting. It also falls into the statement of the Prophet, (صلى الله علیه وسلم):
"O you group of people that believe with your tongues while not with your hearts! Do not abuse the Muslims nor seek after their faults. For indeed, he who seeks after their faults, Allaah will seek after his faults. And whomsoever has Allaah seek after his faults, He will expose them, even if he may have committed them in the privacy of his own home." 
All of this talk is with respect to the scholars that are followed in the Religion. As for the people of innovation and misguidance and those who imitate the scholars but are not from them,  then it is permissible to expose their ignorance and manifest their deficiencies, in order to warn others against following them. 
However, our discussion now is not concerning this topic and Allaah knows best.
 This is an important restricting condition, so memorize it.
 See Al-Kifaayah (pg. 88) of Al-Khateeb, I'laan bit-Tawbeekh Liman dhamma At-Taareekh (pg. 461) of As-Sakhaawee, Sharh Saheeh Muslim (16/144) of An-Nawawee, Majmoo' Ar-Rasaa'il wal-Masaa'il (4/110) of Ibn Taimiyyah and Raf'a-ur-Raibah (pg. 24-27) of Ash-Shaukaanee.
Translator’s Note: Al-Jarh wat-Ta’deel is the Islaamic science of determining whose reports and testimonies are to be accepted and whose are not. Those who fall under the category of Al-Jarh are the ones who are criticized and discredited, such as weak narrators, liars, etc. Those who fall under the category of At-Ta’deel are those whom the scholars have approved of and considered reliable in speech and trustworthy in narration.
 Translator’s Note: This is not a criticism against those who are constantly engulfed in worship. Rather it is a warning for those who may be deceived by their appearance. For indeed it is common that many people when they see someone who exceeds in performing worship, they automatically assume that he is knowledgeable. But most of the times this is not the case. So one must be careful because there does exist a difference between the 'Aalim (scholar) and the 'Aabid (worshipper), as the Prophet, (صلى الله علیه وسلم), said:
"The virtue of the scholar over the worshipper is like the virtue of the moon over the all the stars." (Abu Dawood: 3641, At-Tirmidhee: 2683 and others)
 Consider these great words, O reader and may Allaah have mercy on you, and apply them to the condition of the Muslims today!
 So therefore, these matters are not from the fabrications of some "people" but rather they are nothing more than the actions of the scholars of the past!
 See the story of Al-Haafidh Ad-Daaraqutnee who corrected the Haafidh, the Imaam Ibn Al-Anbaaree when he was young. And he (Ibn Al-Anbaaree) was an elder and respected Imaam, but yet he still accepted the correction from him. The story is found in Taareekh Baghdaad (3/183)
 Surat-un-Nisaa: 20
 Reported by Abu Ya'laa in his Musnad-ul-Kabeer from the path of Mujaalid Ibn Sa'eed and he is very weak. Al-Baihaqee also reported it and its chain or narration is broken. 'Abd-ur-Razzaaq reported it and in its chain is Abul-'Ujfaa As-Sulamee and he is weak also. See Al-Maqaasid-ul-Hasanah (pg. 320).
 It is found in the previous story itself.
 See I'laam-ul-Muwaqqi'een (2/363) and Iqaadh Himam Uleel-Absaar (pg. 100)
 See his book Ar-Risaalah (no. 598-599) and Al-Maqaasid-ul-Hasanah (pg. 15).
 Surat-un-Nisaa: 82
 This is not in the unrestricted sense. See the great scholar Ibn Al-Qayyim's refutation of those who say, "There is no rejection to be done on the issues in which there is difference of opinion" included in I'laamul-Muwaqqi'een (3/288), for it is very important.
 These words ought to be written in gold ink, so consider them!!
 More than one of the Companions have reported this hadeeth, among them Tameem Ad-Daaree. It is transmitted by Muslim (55), Abu Dawood (4944), An-Nasaa’ee (7/156), Ahmad (4/102), Abu 'Uwaanah (1/36-37), Al-Humaidee (837), Al-Baghawee (3514), At-Tabaraanee in Al-Kabeer (1260-1262), Ibn Hibbaan in Raudat-ul-'Uqalaa (194), Ibn An-Najaar in Dhail Taareekh Baghdaad (2/193 & 301) Ash-Shihaab Al-Qadaa'ee in his Musnad (17-18), Wakee' in Az-Zuhd (346 & 621), Abu 'Ubaid in Al-Amwaal (9) and Al-Bukhaaree in At-Tareekh-us-Sagheer (2/35)
 With this wording, the hadeeth has been reported by Ahmad (1/447), Al-Baghawee (2388) and Al-Haithamee in Al-Majma' (5/3) and he said that its narrators were of the standard of the Saheeh. The source of this story occurs in Saheeh Al-Bukhaaree (9/415) and in Saheeh Muslim (1484).
 Translator's Note: The 'iddah (waiting period) before a woman can remarry is 4 months and ten days. But if she is pregnant, then the her waiting period is whichever of the two comes first - either the four months and ten days or the day of her delivery. So if she delivers before the four months pass by, then the time of delivery take precedence and she is allowed to remarry from this point on.]
 These are well known Fiqh issues.
 Translator's Note: When a woman is divorced three times by her husband, he cannot remarry her unless she first marries someone else, has intercourse with him, and then is divorced by him. Only then is she permissible for her first husband again. The weak opinion mentioned above states that the woman that was divorced three times by her husband, in order to become halaal (permissible) for him again, she just needed to remarry another man, without having intercourse with him (i.e. upon the marriage contract alone), and get divorced from him. And Allaah knows best.
 Reported by Abu Ya'laa in his Musnad (1675) and Abu Nu'aim in Ad-Dalaa'il (356) on the authority of Al-Baraa', (رضي الله عنه). Al-Haithamee (رحمه الله) said in Al-Majma' (8/93): "Abu Lailaa reported it and its narrators are all reliable. It has also been reported from the hadeeth of Abu Barzah, (رضي الله عنه), with a strong chain of narration in Ahmad (4/421 & 424) and Abu Dawood (4880).” And in this section occurs the hadeeth of Ibn 'Umar with a hasan chain of narration in At-Tirmidhee (2033), Al-Baghawee (3526) and Ibn Hibbaan (1494 of the Mawaarid). See also At-Targheeb wat-Tarheeb (3/177) of Al-Mundhiree.
 And in these days, how many people exist who imitate the scholars yet are not from them. They deceive the people by making beautiful expressions and using nice words!!
 Translator’s Note: This is an important principle that the Shaikh mentions before continuing further in his book, since he does not want his readers to think that this discussion concerns innovators. Rather, as he states, their affair is to be publicized so that they may be abandoned and rejected. So the discussion here does not apply to them in the least nor can it be used in defense of one of them.