Christians believe that the Bible is the authoritative word of God. Consistent Christians don’t pick and choose what to believe in the Bible, but know the whole thing is “breathed out” by God (2 Timothy 3:16). However, many Christians are pretty embarrassed about the Old Testament. They just don’t know what to do with it or how it connects with Jesus Christ. The Old Testament law contains many commands that not only seem arbitrary and weird, but also downright immoral by our standards: such as the commands to stone people who commit certain sins, sacrifice animals, or to avoid eating pork. We don’t practice these things anymore, but why? A popular tactic that many non-Christians use to argue against Christians is to quote certain commands that sound immoral and tell them that they’re being inconsistent by not following those commands. If Christians are being inconsistent in what they believe in the Bible, then their highest authority is their own opinions, not Scripture. Are Christians being inconsistent by not following many OT laws?
God meant for the Mosaic law to be binding to Israel alone at a specific time in history. It was a temporary covenant that would one day be replaced by a new one. Through the prophet, Jeremiah, God says:
Behold, the days are coming, declares the Lord, when I will make a new covenant with the house of Israel and the house of Judah, not like the covenant that I made with their fathers on the day when I took them by the hand to bring them out of the land of Egypt, my covenant that they broke, though I was their husband, declares the Lord.”
Paul argues that when you put your faith in Christ, you “died to the law through the body of Christ, so that you may belong to another, to him who has been raised from the dead, in order that we may bear fruit for God,” (Rom. 7:4). When we put our faith in Christ, we die to ourselves and live in Christ (Gal. 2:20). Just as a woman is no longer bound to her husband by covenant when he dies, so we are no longer bound by the covenant of the law when we “die.” We are given to Christ, where we are placed under grace instead of the law.
But Jesus says to his disciples, “Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them,” (Matt. 5:17). So if Jesus didn’t abolish the law, is it still applicable to us? No, in the second part of the verse He clearly states He came to fulfill the law. Before Christ, we had to sacrifice animals to atone for our sins, which doesn’t fully cure our sin problem (Heb. 10:4). Christ came and died once for all sin, so that sacrifice is no longer necessary (Rom. 6:10). Before Christ, we needed a temple to worship God and to express His utter holiness and separation from sinners, but after Christ our bodies have become temples of the Holy Spirit (1 Cor. 6:19). Before Christ, God worked with a nation ruled by God. Israel was essentially a theocracy, which is why breaking the religious laws could lead to judicial punishment. After Christ, God doesn’t just work with a single nation anymore, but with the church, which is a sojourner within the nations that welcomes all people.
In conclusion, it isn’t because of inconsistency that Christians don’t follow much of the OT law, but because of good theology. The OT is still important for revealing who God is, how God works up to the time of Christ, and even for moral teachings, but the ceremonial and judicial aspects of the law are not binding to us anymore.