Eighteen denunciations did Isaiah make against the people of Israel, and he recovered not his equanimity until he was able to add, "The child shall behave himself proudly against the ancient, and the base against the honorable" (Isa. iii. 5).
Chaggigah, fol. 14, col. 1.
The Rabbis have related that there was once a family in Jerusalem the members of which died off regularly at eighteen years of age. Rabbi Yochanan ben Zacchai shrewdly guessed that they were descendants of Eli, regarding whom it is said (1 Sam. ii. 25), "And all the increase of thine house shall die in the flower of their age;" and he accordingly advised them to devote themselves to the study of the law, as the certain and only means of neutralizing the curse. They acted upon the advice of the Rabbi; their lives were in consequence prolonged; and they thenceforth went by the name of their spiritual father.
Rosh Hashanah, fol. 18, col. 1.
Eighteen handbreadths was the height of the golden candlestick.
Menachoth, fol. 28, col. 2.
If a man remain unmarried after the age of twenty, his life is a constant transgression. The Holy One—blessed be He!—waits until that period to see if one enters the matrimonial state, and curses his bones if he remain single.
Kiddushin, fol. 29, col. 2.
A woman marrying under twenty years of age will bear till she is sixty; if she marries at twenty she will bear until she is forty; if she marries at forty she will not have any family.
Bava Bathra, fol. 119, col. 2.