Christians do not live under the Old Covenant that is found in the Old Testament. We live under the New Covenant found in the New Testament. We are led by the Holy Spirit of God that lives in us.
2 Corinthians 3:
4 We are confident of all this because of our great trust in God through Christ.5 It is not that we think we are qualified to do anything on our own. Our qualification comes from God. 6 He has enabled us to be ministers of his new covenant. This is a covenant not of written laws, but of the Spirit. The old written covenant ends in death; but under the new covenant, the Spirit gives life.