It is reported that Abū Ḥāzim Salamah b. Dīnār – Allāh have mercy on him – said:

You cannot be a scholar unless you have three traits: you do not transgress against those above you, you do not look down on those lesser than you, and you do not take any dunyā in return for your knowledge.

Al-Bayhaqī, Shuʿab Al-Īmān 3:282, article 1655.