In On Baptism, Against the Donatists, Augustine says, commenting on the words of Cyprian:

To go on to what he says, “that a bishop should be ‘teachable,'”* adding, “But he is teachable who is gentle and meek to learn; for a bishop ought not only to teach, but to learn as well, since he is indeed the better teacher who daily grows and advances by learning better things;”—in these words assuredly the holy man, endowed with pious charity, sufficiently points out that we should not hesitate to read his letters in such a sense, that we should feel no difficulty if the Church should afterwards confirm what had been discovered by further and longer discussions; because, as there were many things which the learned Cyprian might teach, so there was still something which the teachable Cyprian might learn. But the admonition that he gives us, “that we should go back to the fountain, that is, to apostolic tradition, and thence turn the channel of truth to our times,” is most excellent, and should be followed without hesitation (5.26).


*Both Augustine and Cyprian evidently believed that διδακτικος 1 Tim 3:2 and 2 Tim 2:24 means “teachable.” From what I can tell, the word διδακτος carries more precisely the sense of “teachable.”