6:13 he swore by himself. That God, whose “word is truth” (John 17:17; cf. Titus 1:2), should reinforce the surety of that infallible promise through an oath underscores the permanence and seriousness of the divine promise (Gen. 15:8–21; 22:17). While sinful and fallible human beings “swear by something greater” than themselves (v. 16), God, the highest authority, “swore by himself” (v. 13).