“The wage of the righteous person is life.” In this context, the word “life” means living to the fullest today (not necessarily having lots of material things, but having joy, peace, love, etc.), and also has an eschatological meaning and refers to “everlasting life.”
This verse is the antithesis of Romans 6:23, which says, “The wages of sin is death.” Here, the wage earned by the righteous person is life—a meaningful life here and everlasting life in the hereafter. The verb “is” is supplied, but it was common to leave out the “to be” verb, which would be supplied by the reader (in fact, Hebrew does not have a present tense “to be” verb), and Greek often does the same thing. The “wage…is life” would be the most common way to understand the Hebrew text.
The fullness of Romans 6:23 is that the wages of sin is death, but the “free gift of God is life in the Age to Come in Christ Jesus our Lord.” If Romans says everlasting life is a free gift, why is it called a “wage” here in Proverbs? This is an important point and needs to be understood. Everlasting life is never called a “gift” in the Old Testament; that is a New Testament concept. There has always been the sense that everlasting life is a gift of some sort because there is no way a human could purchase it. However, the Old Testament never called it a gift because people had to maintain their trust in God and their faithfulness to Him throughout their lives in order to receive it (Hab. 2:4). That is why there are so many Old Testament Scriptures that say that “righteous” people attain life. In the covenant world of the Old Testament, a “righteous” person was someone who maintained their covenant agreement with God and trusted Him. An unrighteous person broke their covenant with God and disobeyed Him.
Salvation has always been by trusting God, by “faith.” Faith does not earn salvation; it is a necessary condition for salvation. Today, in the Administration of Grace, we believe “unto” salvation (Rom. 10:10). Our trust does not save us, but it opens the door for God to save us. However, people who lived before Jesus paid for the sins of mankind and before God made the New Birth available had to maintain their trust in God throughout their lives, so it was appropriate that God referred to everlasting life as the “wage of righteousness,” the “wage earned by righteousness.”
[For more on the Administration of Grace, see commentary on Eph. 3:2. For more on the New Birth and the permanence of salvation, see Appendix 1, “The Permanence of Christian Salvation”].
“Sin.” In this verse, sin is both literal in this life and a metonmy of the effect for that which sin results in: punishment.