Abraham son of the Rambam, The Guide to Serving God, Chapter 5, E

Generosity with wisdom entails teaching wisdom to one who aspires to it and is worthy to learn it. As the Transmitters of Tradition explained, “The verse, ‘And you shall teach your children,’ includes students” (Sifrei, Va’Etchanan 9). And in explaining the verse, “See, I have taught you (Deuteronomy 4:5), they said, “Just as I have learned without payment, and you have learned from me without payment, so should you, in future generations, teach without charging a fee” (Nedarim 37a). (pgs 55-56) [Translation by R. Yaakov Wincelberg, edited for gender neutrality. Translated from Judeo-Arabic]