Musar על אבות 5:7

There is one who sits before a wise man and is silent and derives a reward for this, for example, one who intently sets himself to listen. And there is one who is silent, and derives a sin from his silence, for example, one who thinks, "Why should I speak before him, inasmuch as he does not know enough to answer me suitably; he does not know as much as I by a long way." And he should be very careful not to think thus, as our Sages said, "There are seven marks of an uncultured man, and seven of a wise man : the wise man does not speak before him who is greater than he in wisdom; and does not break in upon the words of his fellow; he is not hasty to answer; he asks in accordance with the subject matter, and he answers to the point; he speaks of the first thing first and of the last, last; concerning that which he has not heard, he says ; 'I have not heard'; and he acknowledges the truth — and the reverse of these are to be found in an uncultured man" (Aboth 5:7).