One of the biggest heresies of religion is the false teaching that Christians are under the law.

Often times they misinterpret Matthew 5.17-20 as their foundation for their heresy.

Those verses say this:

17 “Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.

18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.

19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.

20 For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.

That passage of scripture is crystal clear.
The message being:

God is teaching that everyone is required to meet the entirety of the law’s perfect & impossible demands if they are to enter into the kingdom of God. However Jesus fulfilled the law’s perfect demands completely for every child of God (that we could never fulfill), and He’s given us His righteousness as a free gift as well. Jesus Christ is the only Person Who’s ever taught all of the law, and He’s the only One Who’s ever done all of the law. (See also 1 Timothy 1.8-11).

Acts 13.39

And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses.

Therefore only the Lord Jesus Christ is great, and only He is worthy of praise and glory.