Genesis 15:15
9-21. Take me an heifer, &c.—On occasions of great importance, when two or more parties join in a compact, they either observe precisely the same rites as Abram did, or, where they do not, they invoke the lamp as their witness. According to these ideas, which have been from time immemorial engraven on the minds of Eastern people, the Lord Himself condescended to enter into covenant with Abram. The patriarch did not pass between the sacrifice and the reason was that in this transaction he was bound to nothing. He asked a sign, and God was pleased to give him a sign, by which, according to Eastern ideas, He bound Himself. In like manner God has entered into covenant with us; and in the glory of the only-begotten Son, who passed through between God and us, all who believe have, like Abram, a sign or pledge in the gift of the Spirit, whereby they may know that they shall inherit the heavenly Canaan.
Job 5:26
26. in a full age—So "full of days" (Job 42:17; Ge 35:29). Not mere length of years, but ripeness for death, one's inward and outward full development not being prematurely cut short, is denoted (Isa 65:22).
Thou shalt come—not literally, but expressing willingness to die. Eliphaz speaks from the Old Testament point of view, which made full years a reward of the righteous (Ps 91:16; Ex 20:12), and premature death the lot of the wicked (Ps 55:23). The righteous are immortal till their work is done. To keep them longer would be to render them less fit to die. God takes them at their best (Isa 57:1). The good are compared to wheat (Mt 13:30). cometh in—literally, "ascends." The corn is lifted up off the earth and carried home; so the good man "is raised into the heap of sheaves" [UMBREIT]. Proverbs 16:31
31. (Compare Pr 20:29).
if—or, which may be supplied properly, or without it the sense is as in Pr 3:16; 4:10, that piety is blessed with long life. Proverbs 20:29
29. The glory of young men . . . the beauty of old men—Each age has its peculiar excellence (Pr 16:31).