Romans 10:5

For Moses [the lawgiver] writeth that the man that doeth the righteousness which is of the law shall live thereby. [Leviticus 18:5. (Comp. Nehemiah 9:29; Ezekiel 20:11; Ezekiel 20:13; Ezekiel 20:21; Luke 16:27-29; Galatians 3:12) The context indicates that the life promised is merely the possession of the land of Canaan (Leviticus 18:26-29); but Tholuck observes that "among the later Jews, we find the notion widely diffused that the blessings promised likewise involve those of eternal life. Orkelos translates: 'Whosoever keeps these commandments, shall thereby live in the life eternal.' And in the Targums of the Pseudo-Jonathan, Moses' words are rendered: 'Whosoever fulfils the commandments shall thereby live in the life eternal, and his portion shall be with the righteous.'" Paul evidently construes it as being a promise of eternal life. (Comp. Luke 18:18-20) But no man could keep the law. Was, then, the promise of God ironical? By no means. The law taught humble men the need of grace and a gospel, and for all such God had foreordained a gospel and an atoning Christ. But to the proud, the self-righteous, the Pharisaical who would merit heaven rejecting grace and the gospel, the promise was ironical, for "doeth... live," implies that whoso fails, dies (Deuteronomy 27:26; Galatians 3:10; James 2:10). There was, then, righteousness by the law, and such as bad it were ripe for the gospel which it foreshadowed, especially in its continual sacrificial deaths for sin; but there was no self-righteousness by the law, and those who strove for it invariably rejected Christ. Those seeking life by law supplemented by grace found in Jesus that fullness of grace which redeemed from law, but those seeking life by law without grace, failed and were hardened-- Romans 11:5-7]