Midrash su Giobbe 12:11

It was taught that R. Ishmael, the son of R. Jose, said: "The older the disciples of the wise grow, the more wisdom they acquire; for it is written (Job 12, 11.) So is with the ancients, wisdom; and with length of days understanding. As to the ignorant, the older they grow, the more foolish they become; for it is said (Job 12, 20) He removeth the speech from trusty speakers, and taketh away the intelligence of the aged."