Psalm 105:8

He hath remembered his covenant for ever
Another argument of praise taken from the covenant of grace, in which he is our God, and of which he is ever mindful; he remembers his covenant ones, whom he perfectly knows, and never forgets them; he remembers his covenant promises to them, and allows them to put him in remembrance of them; he has respect unto his covenant, and the blessings of it, and bestows them on his people; gives them the sure mercies of David; and he remembers his love, which is the source and spring of all.

The word which he commanded to a thousand generations;
that which is properly a covenant with Christ our head on our account, is a word of promise to us; a promise of grace and glory; a free promise, absolute and unconditional: and this he has "commanded", or ordered, decreed, and determined that it shall stand good, and be punctually performed, "to a thousand generations"; that is, for ever; for all his promises are yea and amen in Christ.