There are many authentic ahadeeth from the Prophet (sal-Allaahu 'alayhe wa sallam) concerned with the command to straighten the rows (for congregational prayer), and so this is rarely hidden from any of the students of (Islaamic) knowledge let alone their teachers. However it remains unknown to many that straightening the rows requires straightening it with the feet, not just the shoulders. Indeed we have often heard some of the Imaams of the Masaajid (Mosques) pointing out - when ordering the people to straighten the rows - that the Sunnah is to do so with the shoulders to the exclusion of the feet! Since this is contrary to what is established in the authentic Sunnah, I thought it necessary to mention some ahadeeth that exist on this topic, as a reminder for whoever wishes to act in accordance with the authentic Sunnah, not being deceived by the widespread customs and habits present in the Ummah.
There are two authentic ahadeeth on this topic: The first is the hadeeth reported by Anas, and the second is that reported by An-Nu'maan ibn Basheer, may Allaah be pleased with them both.
As for the hadeeth of Anas, then it as follows;
The Hadeeth of Anas ibn Maalik:
"Straighten your rows and come close together, for indeed I see you behind my back."
The hadeeth is reported by al-Bukharee [2/176 - al-Fath, Boolaaq edition], Ahmad [3/182 and 263], and al-Mukhallis in al-Fawaa'id [1/10/2], all of them reporting via a number of transmission paths (turuq sing. tareeq) from Humayd at-Taweel who said Anas ibn Maalik narrated to us saying:
"The call for commencing of salaah was made, the Messenger of Allaah (sal-Allaahu 'alayhe wa sallam) turned to us and said..." (then he mentioned the above hadeeth).
Al-Bukhaaree adds in one narration of this hadeeth:
"(He turned to us and said) before pronouncing the opening takbeer..."
Also adding at the end,
"...each of us would adjoin his shoulder with that of his companion (standing next to him) and his foot with that of his companion."
This addition also occurs in the report of al-Mukhallis and Ibn Abee Shaybah [1/351] with the following wording: Anas said:
"...So I saw each of us adjoining our shoulder with those of our companions and also (adjoining) our feet with those of our companions, but if you were to practice this today, a person would flee (from you) like a restless mule."
Its chain of narration (sanad) is also saheeh according to the conditions stipulated by the Two Shaykhs (al-Bukhaaree and Muslim). Al-Haafidh (Ibn Hajr) ascribed this wording to Sa'eed Ibn Mansoor and al-Ismaa'eelee. Al-Bukhaaree gave a chapter heading for this hadeeth by saying: Chapter: 'Adjoining the shoulder with the shoulder and the foot with the foot in the row (for prayer).'
As for the hadeeth of an-Nu'maan (ibn Basheer) then it is as follows:
The Hadeeth of an-Nu'maan ibn Basheer:
"Straighten your rows (he said it three times),by Allaah either you straighten your rows or Allaah will cause conflict between your hearts."
The hadeeth has been selected by Aboo Dawood [no.662], Ibn Hibbaan [no.396], Ahmad [4/276] and ad-Doolaabee in al-Kunaa [2/86] from Abil-Qaasim al-Jadalee Husayn ibnil-Haarith who said; I heard an-Nu'maan ibn Basheer say:
"The Messenger of Allaah turned to us and said..." (then he mentioned the above hadeeth). Then an-Nu'maan ibn Basheer added: "...So I saw each man joining his shoulder; knee and ankle with that of his companion."
The sanad of this hadeeth is saheeh, al-Bukhaaree quoted it in discontinuous (mu'allaq) form in a decided manner (indicating that he considered it authentic). Ibn Khuzaymah also connected its chain of narration in his Saheeh [1/82,83] and al-Mundhiree [at-Targheeb 1/176] and al-Haafidh [al-Fath 2/176] both confirmed this. Ibn Hibaanselected the hadeeth in his Saheeh [14/396 - Mawaarid] reporting through the tareeq of ibn Khuzaymah.
The text of the hadeeth is also reported by ad-Doolaabee by way of Baqeeyah ibn il-Waleed who said:
'Hurayz narrated to us saying: I heard Ghaylaan al-Muqri' narrate from Abee Qutaylah Marthad ibn Wadaa'ah (who said: I heard) an-Nu'maan ibn Basheer say...', (then he mentioned the hadeeth).
There is no problem with the sanad for the purpose of supporting reports (mutaab'aat), its reporters are reliable apart from Ghaylaan al-Muqri'. Perhaps he is Ghaylaan ibn Anas al-Kalbee (their mawlaa) ad-Dimishqee. If that is the case then his condition (as a reporter) is unknown. A group of the reporters have narrated from him and al-Haafidh (ibn Hajr) said about him: 'He is acceptable (Maqbool).' Then it became clear that identifying this reporter in the sanad as al-Muqri' was a mistake, as al-Bukhaaree and ibn Hibaan had said, and that in fact he is Ghaylaan ibn Ma'shar al-Muqraa'ee [Lubaab 3/237]. Ibn Abee Haatim [7/53] has given a biography for him, mentioning that a number of people have reported from him, and Ibn Hibaan [5/290] declared him reliable.
The Fiqh of these Ahadeeth
In these two ahadeeth there are a number of important points of benefit and fiqh.
- The obligation to straighten the rows for salaah and to stand close together in them, due to the command mentioned in the ahadeeth. The rule concerning such commands is that they constitute an obligation (wujoob) except if accompanying evidence (qareenah) proves otherwise as is well established in the science of fiqh principles. The qareenah here in fact emphasizes the obligation, and that is in the saying of the Prophet (sal-Allaahu 'alayhe wa sallam),
"...or Allaah will cause conflict between your hearts,"
since such a warning is never given for leaving that which is not obligatory as is quite clear. 
- The forming and straightening of the rows mentioned in the hadeeth is only achieved by joining the shoulder and the side of ones foot with the shoulder and foot of the adjacent person. This is because that is what the Companions, radiallaahu 'anhum, did when ordered to straighten the rows and stand close together in them. Hence al-Haafidh (ibn Hajar) said in al-Fath after mentioning the additional saying of Anas in the first hadeeth that I have quoted above:"This (wording) is an explicit explanation that the mentioned action (of the Companions) was done in the time of the Prophet (sal-Allaahu 'alayhe wa sallam). With this in mind the usage of this action as a pretext for explaining what straightening the row means becomes complete."
It is regrettable that many Muslims have neglected this Sunnah of straightening the row, or rather they have lost it altogether, except for a few of them. For I have not seen this practiced by any group amongst them except Ahlul-Hadeeth (the People of the Hadeeth). I saw them in Makkah in the year 1368AH enthusiastic and concerned with adhering to the Sunnah as with other Sunan of al-Mustafaa (Muhammad the Messenger of Allaah) (sal-Allaahu 'alayhe wa sallam). This contrary to others from the followers of the Madhaahib - and I do not exclude the Hanaabilah (Hanbalees), for this Sunnah has become utterly forgotten amongst them. In fact they have consecutively abandoned and turned away from it. This is because most of their Madhaahib state that the Sunnah in this regard is that a space of four fingers width should be kept between ones feet, and more than this is disliked, as is detailed in al-Fiqh 'alal-Madhaahib al-Arba'ah [1/207].
This spacing has no foundation in the Sunnah; rather it is based on mere opinion. If it were correct then it would be necessary to restrict this practice to the Imaam and the one praying on his own so that the authentic Sunnah (of standing close in the row) would not be opposed with this practice, as the fundamental principles of fiqh (al-Qawaa'id al-Usooleeyah) necessitates.
In short I appeal to the Muslims - especially the Imaams of the Masaajid, those who are concerned to follow the Prophet (sal-Allaahu 'alayhe wa sallam), and to acquire the virtue of reviving his Sunnah, I appeal to them to act by this Sunnah, have concern for it, and call the people to it until they unify upon it, and by what they will be saved from that warning "or Allaah will cause conflict between your hearts." 
I add in this addition  (of my book): It has reached from one of the callers to Islaam (du'aat) that he belittles the status of the Sunnah that the Companions practiced, and which they did so with approval of the Prophet (sal-Allaahu 'alayhe wa sallam). He insinuates that the Prophet (sal-Allaahu 'alayhe wa sallam) did not teach them this practice. So he has not realized - and Allaah knows best - that:
- this was their understanding and that
- the Prophet (sal-Allaahu 'alayhe wa sallam) approved of their understanding and their practice.
This is sufficient amongst Ahlus-Sunnah to affirm the legitimacy of this practice, because the witness sees what the absent does not, and the Companions are people whose followers will never be wretched (unsuccessful).
- In the first hadeeth there is an affirmation of a clear miracle (mu'jizah) given to the Prophet (sal-Allaahu 'alayhe wa sallam), and that was his ability to see behind him without turning his head. However it should be known that this was exclusively for the Prophet (sal-Allaahu 'alayhe wa sallam) when he was in Salaah since nothing exists in the Sunnah that states that he used to see behind him without turning his head outside the Salaah. And Allaah knows best.
- In the two ahadeeth there is a clear proof for something that many people do not know about, although it has become recognized in the field of psychology, and that is the fact that outer (apparent) evil and corruption affects inner evil and corruption and vice versa. There are many ahadeeth about this, perhaps we will undertake the task of gathering and referencing them at some later opportunity if Allah, The Most High wishes.
- The entering of the Imaam into the opening takbeer for prayer when the mu'ahddhin says 'The Prayer is about to start.' (qad qaamati-salaah) is an innovation in the religion (bid'ah) due to its contradicting the authentic Sunnah, as these ahadeeth prove - especially the first one. The ahadeeth show us that after the Iqaamah has been called there is a duty upon the Imaam which he must fulfill, and that is commanding the people to straighten the rows, reminding them of that, for he is responsible for them and will be asked.
"...And all of you are shepherds and all of you will be asked about your flock."
 Translated from Silsilatul-Ahadeethis-Saheehah of Shaykh Muhammad Naasirud-Deen Al-Albaanee. Vol.1 pp70-74, Hadeeth no.31 and 32.
 Translators Note: Standing close in the row, filling the gaps and straightening the line carries a great reward and virtue as well as being obligatory. This is mentioned in a number of ahadeeth, like the following:
"The best of you are those who stand with their shoulders closest (to the one standing next to them) in the salaah, and there is no step greater in reward than that taken by a man toward a gap in the row thus filling it." [Reported by at-Tabaraanee in al-Aswat, refer to Saheeh at-Targheeb wat-Tarheeb (1/200)]
"Whoever fills a gap in the row, Allaah raises him up due to it a rank and builds a house for him in al-Jannah." [Reported by at-Tabaraanee in al-Aswat and al-Asbahaanee in at-Targheeb, the hadeeth is saheeh as occurs in Saheeh at-Targheeb (no.505)]
 Translators Note: There are a number of ahadeeth that explain the virtue of reviving the Sunnah and the calling the people to guidance and righteousness.
For example the Prophet (sal-Allaahu 'alayhe wa sallam) said:
"Whoever calls to guidance will have the same reward as all those who follow him in that guidance but this will not take anything away from their reward. Whoever calls to untruth will carry the same sin as all those who follow him in that, but that will not take anything away from their sins." [Reported by Ahmad in his Musnad, Muslim in his Saheeh and others]
 Translators Note: This article is taken from the newest edition.