Not only among Christians but we also find unbelievers who accuse Christians of picking and choosing the parts of the Old Testament that they want to follow.
If we look at the life of Jesus on the earth, this was one area where the religious leaders of the time always seemed to find fault with Jesus ie he did not seem to keep the Sabbaths in the way they were used to, his disciples did not wash hands the way tradition commanded them etc. While the law stated that lepers were unclean and treated as untouchables, Jesus seemed to have no problems touching them. While the law commanded that adulterers were to be stones, all Jesus told the woman who was caught in adultery was "Neither do I condemn you. Go and sin no more".
We might be justified in asking the question, "was Jesus not keeping the law of Moses"?
But yet we find Jesus making this statement in Matt 5:17 - "I have not come to abolish the law"
What did Jesus mean?
If we look at Matt 23:23- we find Jesus accusing the Pharisees of "neglecting the more important matters of the law" even while they went to the extent of giving a tenth of everything they had to the Lord. In other words, Jesus was saying that there were areas in the law which were more important and while the Pharisees went by the letter of the law or the written "content", there was an unwritten "intent" which God was more interested in and which is superior. In this case, Jesus mentions these qualities as justice, mercy and faithfulness.
If we read Matt 5:21-48, we find that Jesus takes various examples ie murder, adultery, divorce, oaths, revenge etc. In each case Jesus establishes that God is looking for more than merely keeping the written law but instead he looks at our hearts to evaluate our true condition. It is the same principle he presents in Matt 12:3 where he mentions that David did what was not "lawful" ie ate the consecrated bread which was only to be eaten by the priests. Jesus goes on to say that an inward quality of mercy is of more value than outward sacrifice for "man looks at the outward appearance but God looks at the heart".
If we come to the book of Acts 15, we find the same teaching advocated by the early church when there was a controversy regarding whether gentiles needed to be circumcised in order to be saved- salvation is through Grace by faith and is not dependent on external actions. It is true that there are certain deeds that accompany that faith i.e helping those in need, loving our neighbour etc but those are merely an outcome of our faith and do not make us any more deserving of salvation.
Take the example of tithing which is clearly an old testament principle. When we come to the NT, we are no longer to limit our giving to 10%. It is to be based on our ability and even beyond our ability (2 Cor 8:3). The early believers sold their lands and the proceeds of these were used to help the poor/support churches in need etc. All these were motivated by the love of the Lord and the desire to help anyone in need not expecting anything in return - so contrary to the teachings on giving we hear today where we are prompted to give so that "God will bless us in return". God is faithful and he will certainly supply all our needs but we need to remember that he gives us wealth so that we can in turn help those in need and not hoard up the same for ourselves. May the Lord enable us to be wise stewards of all that he gives into our care- that means our giving needs to go where the labourers are and where the harvest is. May our treasures not be laid up on this earth where it perishes so easily but let our eyes be fixed on heaven where our true riches ought to be.
To sum up, we live under the new covenant which is not driven by "customs" and "practices" but instead by "attitudes" and "intents" for God sees our heart. It is superior because the demands are higher - sin is not sin when we commit it, it is sin even before that i.e when we contemplate it in our hearts. Hence the command to "guard our hearts with all diligence". Praise be to God that we are not expected to keep the demands on the new covenant on our own strength because that is impossible. Instead He has given us His Holy Spirit who resides within us to teach us the way to walk and live out a godly life from inside-out. What a wonderful counsellor we have!
God Bless!