Romans 10:5

For Moses writeth that the man that doeth the righteousness which is of the law shall live thereby.

This quotation from Leviticus 18:5 is further indication that the "righteousness" in view here regards keeping God's commandments. The person who kept that ancient law was indeed righteous, a fact which is modified by the truth that none save Jesus Christ ever kept it perfectly. Even the ascription of righteousness to Zacharias and Elizabeth, cited above, must be understood in a relative, not an absolute, sense. The mountain fact concerning Christ is that he indeed kept the law perfectly, his faith and obedience reaching a state of absolute perfection for every second of his total life on earth. That is what God requires to save any man. That is the righteousness which alone can save; and it is available to people "in Christ"; the great device of God's redemption plan being not that of transferring righteousness into sinners, but that of transferring sinners into Christ, where the righteousness is.