Charles H. Spurgeon on Psalms 103:18

Children of the righteous are not, however, promised the Lord's mercy without stipulation, and this verse completes the statement of the last by adding: To such as keep his covenant, and to those that remember his commandments to do them. The parents must be obedient and the children too. We are here bidden to abide by the covenant, and those who run off to any other confidence than the finished work of Jesus are not among those who obey this precept; those with whom the covenant is really made stand firm to it, and having begun in the Spirit, they do not seek to be made perfect in the flesh. The truly godly keep the Lord's commands carefully —they "remember"; they observe them practically —"to do them": moreover they do not pick and choose, but remember "his commandments" as such, without exalting one above another as their own pleasure or convenience may dictate. May our offspring be a thoughtful, careful, observant race, eager to know the will of the Lord, and prompt to follow it fully, then will his mercy enrich and honour them from generation to generation. This verse also suggests praise, for who would wish the Lord to smile on those who will not regard his ways? That were to encourage vice. From the manner in which some men unguardedly preach the covenant, one might infer that God would bless a certain set of men however they might live, and however they might neglect his laws. But the word teaches not so. The covenant is not legal, but it is holy. It is all of grace from first to last, yet it is no panderer to sin; on the contrary, one of its greatest promises is, "I will put my laws in their hearts and in their minds will I write them"; its general aim is the sanctifying of a people unto God, zealous for good works, and all its gifts and operations work in that direction. Faith keeps the covenant by looking alone to Jesus, while at the same time by earnest obedience it remembers the Lord's commandments to do them.