Do you believe in following the 10 Commandments from the OT? Is it sin if you don’t?
The OT commandments were given to Israel as part of The Law. We are not bound to that Law. We are under the law of Christ.
Check out the sermon on the mount. Jesus charges not just doing the action, but thinking it makes it a sin.
You have heard that it was said by them of old time, Thou shalt not kill; and whosoever shall kill shall be in danger of the judgment: But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of judgment . . . . (Matt. 5:21-22).
You have heard that it was said by them of old time, Thou shaft not commit adultery: But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart (Matt. 5:27-28).
Again, you have heard that it hath been said by them of old time, Thou shall not forswear thyself, but shalt perform unto the Lord chine oaths: But I say unto you, Swear not at all . . . (Matt. 3:33-34).
Other contrast between what Jesus taught and what Moses said or what Moses' interpreters said are found in Matt. 5:38-39, 43-44.
In each of these, the authority of Jesus Christ is placed beside that of Moses in such a way that people could see that what Jesus taught was superior to that which was revealed through Moses.