In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Muslim [rahimahullaah] said: know-may may Allaah [The Most High] grant you success-that it is obligated on everyone [i.e. the scholars who criticise and commend narrators of hadeeth] to know the distinction between the authentic chains of transmission and the faulty ones; [the distinction between the trustworthiness, precision etc] of the narrators of [the authentic chains] and those who have been charged [with weakness, forgetfulness, fabrication etc in their narrations], so that nothing is transmitted from these narrations except that which whose narrator is trustworthy and blameless in his narrations, and avoid that which is from those who have been charged with [weakness, forgetfulness, fabrication etc], and the obstinate ones amongst Ahlul Bidah. [Ref 1]
Shaikh Saaleh Aala Shaikh [hafidhahullaah] said: Giving importance to the Sunnah and refuting the innovators is [something] manifest from the Imaams of Islaam. Indeed, they [devoted] their lives in refuting the innovators, but not the ‘Kuffaar Asliyyeen’ [i.e. those who do not ascribe themselves to Islaam]. And if you look at the statements of Imaam Ahmad, Sufyaan, Hammaad Bin Zayd, Hammaad Bin Salamah, Nu-aym Ibn Hammaad, Al-Awzaa’ee, Ishaaq, Ali Ibn Al-Madeenee and their likes amongst the Imaams of the Sunnah, you will find that their speech and striving was [devoted] in refuting the innovators and declaring their principles faulty, even though they [i.e. the innovators] were still within the fold of Islaam. They [i.e. the Imaams of the Sunnah] did not busy themselves with refuting the Jews, the Christians and others [instead they refuted the innovators within Islam], because the evil of the innovators is not manifested to the people of Islaam and the people of Islaam are not safe from it. As for the Kaafir Asliy [i.e. the one who does not ascribe himself to Islaam], the harm in [his religion] is manifest and clear to every Muslim. [Ref 2]
Shaikh Rabee Bin Haadi [hafidhahullaah] said: The virtue of knowledge is very great indeed. It is obligated on the scholars to honour this knowledge, act upon you it, be sincere to Allaah about it [i.e. when seeking, teaching and acting upon it], and likewise the students of knowledge [should be the same]. It is obligated on the scholars to give out the knowledge they possess; and when they are asked [questions], it is obligated on them to respond. Allaah [The Most High] said: [ إِنَّ الَّذِينَ يَكْتُمُونَ مَا أَنزَلْنَا مِنَ الْبَيِّنَاتِ وَالْهُدَىٰ مِن بَعْدِ مَا بَيَّنَّاهُ لِلنَّاسِ فِي الْكِتَابِ ۙ أُولَٰئِكَ يَلْعَنُهُمُ اللَّهُ وَيَلْعَنُهُمُ اللَّاعِنُونَ – Verily, those who conceal the clear proofs, evidences and the guidance, which We have sent down, after We have made it clear for the people in the Book, they are the ones cursed by Allah and cursed by the cursers. [Surah Al-Baqarah Aayah 159]
Likewise, it is obligated on them to act [upon this knowledge]. Allaah said:
يَا أَيُّهَا الَّذِينَ آمَنُوا لِمَ تَقُولُونَ مَا لَا تَفْعَلُونَ
كَبُرَ مَقْتًا عِندَ اللَّهِ أَن تَقُولُوا مَا لَا تَفْعَلُونَ
O you who believe! Why do you say that which you do not do? Most hateful it is with Allah that you say that which you do not do. [Surah Saff’ Aayah 2-3]
If a scholar urges people towards knowledge, action and sincerity, then it is obligated on him to be the first person to hasten towards righteous deeds, sincerity to Allaah and to sanctify this knowledge, lest this statement of Allaah applies to him: [ كَبُرَ مَقْتًا عِندَ اللَّهِ أَن تَقُولُوا مَا لَا تَفْعَلُونَ – Most hateful it is with Allah that you say that which you do not do].
Allaah informed us that some of the Prophets said to their people: [ وَمَا أُرِيدُ أَنْ أُخَالِفَكُمْ إِلَىٰ مَا أَنْهَاكُمْ عَنْهُ – I wish not, in contradiction to you, to do that which I forbid you]. [Surah Hud’ Aayah 88]. This was said by Shu’aib [alayhis salaam] and every Prophet also said this. It is obligated on a scholar to refrain from desiring the worldly possessions of the people – neither desiring status nor position, neither authority nor to put in charge of some workplace. He should not desire anything through that knowledge except Allaah’s Countenance. see here: https://salaficentre.com/2019/10/sincerity-certificates-of-knowledge-and-the-purpose-behind-knowledge-by-shaikh-uthaymeen-rahimahullaah/
It is obligated on him to call the people to the path of Allaah and spread knowledge in the Ummah. Allaah said:
قُلْ هَٰذِهِ سَبِيلِي أَدْعُو إِلَى اللَّهِ ۚ عَلَىٰ بَصِيرَةٍ أَنَا وَمَنِ اتَّبَعَنِي ۖ وَسُبْحَانَ اللَّهِ وَمَا أَنَا مِنَ الْمُشْرِكِينَ
Say (O Muhammad): “This is my way; I invite unto Allah (i.e. to the Oneness of Allah – Islamic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allah i.e to the Oneness of Allah – Islamic Monotheism) with sure knowledge. And Glorified and Exalted be Allah (above all that they associate as partners with Him). And I am not of the Mushrikun (polytheists, pagans, idolaters and disbelievers in the Oneness of Allah; those who worship others along with Allah or set up rivals or partners to Allah). [Surah Yoosuf’ Aayah 108]
Allaah said: [ ادْعُ إِلَىٰ سَبِيلِ رَبِّكَ بِالْحِكْمَةِ وَالْمَوْعِظَةِ الْحَسَنَةِ ۖ وَجَادِلْهُم بِالَّتِي هِيَ أَحْسَنُ – Invite (mankind, O Muhammad) to the Way of your Lord (i.e. Islam) with wisdom (i.e. with the Divine Inspiration and the Qur’an) and fair preaching, and argue with them in a way that is better]. [Surah An-Nahl’ Aayah 125]
Therefore, it is obligated on a scholar to be a caller to the path of Allaah [The Blessed and Most High]. By Allaah! Teaching is among the greatest means of calling to the path of Allaah. The Messenger [sallal laahu alayhi wasallam] was the leader of the callers to the path of Allaah. The people use to come to him in the masjid and at his house. He was the greatest caller to the path of Allaah and the greatest conveyor of Allaah’s religion.
It is obligated on us to convey. We are inheritors of the knowledge left behind by the Prophets. We are students of knowledge, and I do not say that we are from the scholars; but we have a share of what we have learnt from the inheritance of the Prophets; therefore, it obligated on us to convey it. So, let us be callers to the path of Allaah – conveying from what Allaah has revealed and from the Messenger of Allaah of Allaah [sallal laahu alayhi wasallam]. And propagating the message necessitates speech and action – calling to the path of Allaah with speech and action [i.e. act upon what we say]. This affair is obligatory, so let us strictly adhere to it, act upon it and fulfil it, and beware of opposing your statements with your actions. [Ref 3]
[Ref1: An Excerpt from Muqaddimah Saheeh Muslim: page 61]; [Ref 2: An Excerpt from Sharh Lum-atil Ittiqaad: page 155. Slightly paraphrased]; [Ref 3: Source: An Excerpt from Marhaban Yaa Taalibal Ilm’ page 132-136. d slightly paraphrased]