And from this understanding, is what Abu Nu’aim and others have reported from Kumail Ibn Ziyaad  on the authority of ‘Alee, (رضي الله عنه), that he said:
“The people are of three types: the learned scholar, the student of knowledge who is upon the path towards salvation and the uncivilized ignorant follower following every ideology, blowing in the direction of every wind. He is not guided by the light of knowledge nor is he established upon a firm pillar.”
Then he mentioned some words on the benefit of knowledge, up to the point where he said:
“Here! Indeed, here is immense knowledge – and he pointed to his chest – if only I could gather those who would carry it!
But yes, instead I have found he who is unreliable and not to be entrusted with it. Doing the works of the Religion for the sake of this worldly life, making a demonstration of the favours of Allaah (i.e. the knowledge he was given) in front of His servants and using His arguments against His beloved ones (the true scholars).
Or he is one who is honest and obedient towards the carriers of truth, while possessing no understanding and insight (of his own) in his mind. Doubt has pierced his heart and troubled it upon the first time problems were presented to it. Indeed, he is neither this nor that.
Or he is one who is greedy for fulfilling his pleasures. He has become submissive to the guidance of his desires or infatuated with the piling up of wealth and treasures. These individuals are not from among the shepherds of the Religion in any way. The closest things in resemblance to them are the cattle that graze about freely. Just like that, the knowledge has died with the death of its carriers. 
O Allaah! Verily, do not isolate on this earth, he who establishes the evidences for Your sake, whether he be apparent and well known or fearful and obscure in order that the evidences and clear proofs of Allaah may not be refuted.
And how many of them are there? Where are they? I swear by Allaah, they are the fewest in number, yet the greatest in stature in the sight of Allaah. Allaah preserves His evidences and manifest proofs through them until their likes desist from it and plant it into the hearts of those similar to them.
Through them, knowledge is fortified upon the reality of evidences. And they spread the glad tidings of the spirit of certainty. They soften what those who give in to excessiveness have roughened. And they draw close to that which the ignorant feel repelled by and estranged from.
They accompany the world with their bodies while their souls are drawn towards the great abode. They are Allaah’s aides on His earth and the callers towards His Religion. And they long for their look (at Him in Paradise)." 
 He is Kumail Ibn Ziyaad An-Nakha’ee (رحمه الله). He was one of the righteous and noble amongst the Taabi’een. He was captured and killed by Al-Hajaaj Ibn Yoosuf Ath-Thaqafee in 82H. See Al-Ma’rifah wat-Taareekh (2/481) of Al-Fasawee (رحمه الله).
 The great scholar Ibn Abeel-'Izz Al-Hanafee (رحمه الله) said in his book Al-Itibaa' (pg. 86):
"In this narration, the Commander of the Believers has divided the blameworthy carriers of knowledge into three categories:
- The wicked innovator who is not trustworthy and has no Eemaan. He is the one who rejects the truth which the Book came with, despises the creation and argues about the verses of Allaah without any authority. There is only pride in his heart
- the blind-follower that follows without any clear guidance or certainty, and
- the one who follows the desires of the body and wealth."
 This report has been transmitted by Abu Nu’aim in Al-Hilyah (1/79) and Al-Khateeb in Al-Faqeeh wal-Mutafaqqih (1/49). Also see Jaami’ Bayaan-ul-‘Ilm of Ibn ‘Abd-il-Barr (2/112) and Al-Bidaayah wan-Nihaayah of Ibn Katheer (9/47). Shaykh Saleem Al-Hilaalee mentioned it in one of his articles in Al-Asaalah magazine (Sha’abaan issue no. 3 of 1413H).