Jamieson, Fausset and Brown on Titus 2:4

4. to be sober--Greek, "self-restrained," "discreet"; the same Greek as in Tit 2:2, "temperate." (But see on Tit 2:2; compare Note, 2Ti 1:7). Alford therefore translates, "That they school (admonish in their duty) the young women to be lovers of their husbands," &c. (the foundation of all domestic happiness). It was judicious that Titus, a young man, should admonish the young women, not directly, but through the older women.