Mishnà su I Cronache 29:78

Rabbi Elazar of Bartotha said: give to Him of that which is His, for you and that which is yours is His; and thus it says with regards to David: “for everything comes from You, and from Your own hand have we given you” (I Chronicles 29:14). Rabbi Jacob said: if one is studying while walking on the road and interrupts his study and says, “how fine is this tree!” [or] “how fine is this newly ploughed field!” scripture accounts it to him as if he was mortally guilty.

He used to say: At five years of age the study of Scripture; At ten the study of Mishnah; At thirteen subject to the commandments; At fifteen the study of Talmud; At eighteen the bridal canopy; At twenty for pursuit [of livelihood]; At thirty the peak of strength; At forty wisdom; At fifty able to give counsel; At sixty old age; At seventy fullness of years; At eighty the age of “strength”; At ninety a bent body; At one hundred, as good as dead and gone completely out of the world.