If we demonstrate that we trust God about how we are to live through following his instructions, then we are living by faith. God's instructions have always been meant to be obeyed by faith in a way that builds a relationship between Him and His people, however, God's instructions can be obeyed for reasons other than faith, such as legalism, and God has always disdained it when His people outwardly obeyed His instructions while their hearts were far from Him (Isaiah 29:13, Mark 7:6-13). The problem was not that God gave Israel faulty instructions for how to live and that Israel did not obtain righteousness because they obeyed what God told them to do, but rather the problem was that they pursued God's instructions in the wrong way, as if righteousness were by works rather than by faith.
God is holy, righteous, and good, and He gave instructions for how to live in accordance with his character, so to say that those instructions have been ended is to say that God's holiness, righteousness, and goodness have ended. Rather, Messiah is the goal of God's instructions because they are all about him, he is the one who can pay our penalty for disobeying them, and He is the one who can cause us to obey them, thereby meeting their righteous requirement (Romans 8:4).