Robert Traill (The Throne of Grace), Works 1:193:
Grace can revive the decayed state of a believer: Ps. 23:3, He restoreth my soul. He reneweth their strength, Isa. 40:31. Thy youth is renewed like the eagles, Ps. 103:5. This is impossible in nature, and as to our bodies; but as to our souls, and the work of God in them, it is what is promised, and often done. Old people may, and do often, in their folly and vanity, counterfeit youth; but all their arts cannot make themselves one hour younger. But the Lord can renew the youth of the new creature, and make it better with him than ever it was. David prays for it, Ps. 51:10, Create in me a clean heart, O God; and renew a right spirit within me. Peter got a new conversion, Luke 22:32. They both had been converted and renewed before; but they fell under a sad decay, and needed this restoring grace, and got it.
Grace can revive the decayed state of a believer: Ps. 23:3, He restoreth my soul. He reneweth their strength, Isa. 40:31. Thy youth is renewed like the eagles, Ps. 103:5. This is impossible in nature, and as to our bodies; but as to our souls, and the work of God in them, it is what is promised, and often done. Old people may, and do often, in their folly and vanity, counterfeit youth; but all their arts cannot make themselves one hour younger. But the Lord can renew the youth of the new creature, and make it better with him than ever it was. David prays for it, Ps. 51:10, Create in me a clean heart, O God; and renew a right spirit within me. Peter got a new conversion, Luke 22:32. They both had been converted and renewed before; but they fell under a sad decay, and needed this restoring grace, and got it.