Keep my decrees and laws, for the person who obeys them will live by them. I am the Lord. (Lev. 18.5 NIV)
Paul, as a Pharisee, recognized the promise of eternal life in Lev. 18.5. Before he was a Christian, Paul, in his conception of this verse, would probably sacrifice as needed to keep his slate clean in anticipation of the resurrection. Thus Heb. 2.15 (and free those who all their lives were held in slavery by their fear of death-NIV) speaks of those in slavery to death because of noncompliance of the Mosaic Law (besides the 10 Commandments, all the obligations of observance such as Sabbaths, 3 Yearly feasts, dietary restrictions, and more). Heb.2.14 argues that Christ’s purpose was to render the devil powerless: Since the children have flesh and blood, he too shared in their humanity so that by his death he might break the power of him who holds the power of death—that is, the devil (NIV). Previously, Satan could accuse any for falling short especially if, for instance, they didn’t fast and give the half shekel yearly on the Day of Atonement where sins were remembered yearly (see Heb. 10.1-3 and the use of “annual”).
Jesus is the “Stronger man” than the devil in the parable found in Lk. 11.22: But when someone stronger attacks and overpowers him, he takes away the armor in which the man trusted and divides up his plunder (NIV). Also, Col. 2.14-15 speaks of the debt of obligation which, taken away, leaves the adversary powerless: having canceled the charge of our legal indebtedness, which stood against us and condemned us; he has taken it away, nailing it to the cross. And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross (NIV).
Therefore, when looking at Paul’s use of Lev. 18.5 in Rom. 10.4-5, we see that the fulfillment of the Law is accomplished by Christ since He kept it perfectly. Now, after His sacrifice of death for sins not His own, He deserves resurrection based on Lev. 18.5, and represents Christians to the Father. Folks seeking salvation by attempting to keep the Law have a burden that is impossible to bear: a yoke that neither we nor our ancestors have been able to bear (Acts 15.10b NIV).
Notice the claim of Jesus in Jn. 8.26- “Which of you can prove me guilty of sin?” The man, Jesus, was sinless, and so was granted eternal life in the flesh after His atonement for our sins. Gal. 3.19, referring back to vs. 12, indicates this promise of Lev. 18.5, was meant for Christ: Why, then, was the law given at all? It was added because of transgressions until the Seed to whom the promise referred had come (NIV). Jesus, as the second Adam, now gives eternal life to those who trust Him. Christians are now free from the charge and accusation of legal indebtedness to the Law’s requirements since we have Christ’s righteousness recorded in our account: For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit (1Pet. 3.18 NIV).