Midrasch zu Mischlej 19:23

R. Jonah in the name of R. Zeira said: "He who passed seven nights [in succession] without dreaming, is to be called wicked, for it is said (Pr. 19. 23.) And he (that hath it) shall abide satisfied: he shall not be visited with evil. Do not read Sabea (satisfied) but read Sheba (seven)." R. Acha, the son of R. Chija and the grandson of R. Abba, said to him, "Thus had said R. Chiya in the name of R. Jochanan: 'He who goes to sleep after he has satisfied himself with the words of the Torah will never be the recipient of bad tidings, as it is said (Ib.) And he [that hath it] shall abide satisfied, he shall not be visited with evil.' "