Kommentar zu Mischlej 23:2

and you shall put a knife into your jaw Heb. בלועך, into your jaw. If you see that he is stingy, do not eat of his [food].

if you are a man with a hearty appetite If you are a glutton and long to eat, it is better that you thrust a knife between your teeth. Our Sages expounded this as referring to a disciple sitting before his teacher. If he knows that his teacher will give him an answer for everything he asks, let him investigate the subtle points and ask concerning his tradition, but if not, let him keep his peace.