Romans 10:5

Μωυσῆς γὰρ γράφει : Moses' authority is unimpeachable on this point. The righteousness that comes from law must be an achievement: the man who has done it shall live in it, Leviticus 18:5. Paul writes ἐν αὐτῇ with reference to δικαιοσύνην : the ἐν αὐτοῖς of the LXX refers to πάντα τὰ κρίματα which precedes. Moses, of course, in writing thus did not mock his people; the O.T. religion, though an imperfect, was a real religion, under which men could be right with God. To keep the law of God and live by doing so (Matthew 19:17) was the natural aim and hope of a true Israelite; only, in this case, the law was not a collection of statutes, but a revelation of God's character and will, and he who sought to keep it did so not alone, but in conscious dependence on God whose grace was shown above all things else by His gift of such a revelation. Paul, however, is writing with Pharisees and legalists in his eye, and with the remembrance of his own experience as a Pharisee in his heart; and his idea no doubt is that this road leads nowhere. Cf. Galatians 3:10-12. To keep the law thus is an impossibility.