4:17 knew his wife . . . bore Enoch. See note on v. 1. In God’s common grace, family life is enjoyed by unbelievers as well as by believers.

he built a city. In seeking the security of a city, it appears that sinful Cain both defied the divine judgment that he should be a vagabond (v. 12) and showed his lack of faith in the protection provided by God’s mark (v. 15). The earthly city provides both civilization and protection, but culminates in the building of a city that challenges God’s supremacy (11:4). The faithful by contrast look for a heavenly city (Phil. 3:20; Col. 3:1–4; Heb. 11:10, 16; 12:22; 13:14).