Christians and the Law

The responsibility of Christians to obey the Law of Moses is a subject
that comes up from time to time, which always surprises me because the
Bible is perfectly clear on the matter.  While it is understandable,
though not excusable, that atheists regularly confuse Christianity with
Judaism when attempting to criticize the former, it is absolutely
bizarre that some Christians are still under the impression that they
have an obligation to abide by Jewish Law.

Christians are not Jews.  Christians are not obligated to follow Mosaic
Law.  Ask any Jew, he should be able to confirm it.  As will the Bible, in Acts 15:

The Council at Jerusalem

Certain people came down from Judea to
Antioch and were teaching the believers: “Unless you are circumcised,
according to the custom taught by Moses, you cannot be saved.”  This
brought Paul and Barnabas into sharp dispute and debate with them. So
Paul and Barnabas were appointed, along with some other believers, to go
up to Jerusalem to see the apostles and elders about this question. The
church sent them on their way, and as they traveled through Phoenicia
and Samaria, they told how the Gentiles had been converted. This news
made all the believers very glad.  When
they came to Jerusalem, they were welcomed by the church and the
apostles and elders, to whom they reported everything God had done
through them.Then
some of the believers who belonged to the party of the Pharisees stood
up and said, “The Gentiles must be circumcised and required to keep the
law of Moses.” 
The apostles and elders met to consider this question. After
much discussion, Peter got up and addressed them: “Brothers, you know
that some time ago God made a choice among you that the Gentiles might
hear from my lips the message of the gospel and believe. God, who knows the heart, showed that he accepted them by giving the Holy Spirit to them, just as he did to us. He did not discriminate between us and them, for he purified their hearts by faith. Now
then, why do you try to test God by putting on the necks of Gentiles a
yoke that neither we nor our ancestors have been able to bear? No! We believe it is through the grace of our Lord Jesus that we are saved, just as they are.”
The whole assembly
became silent as they listened to Barnabas and Paul telling about the
signs and wonders God had done among the Gentiles through them. When they finished, James spoke up. “Brothers,” he said, “listen to me. Simon has described to us how God first intervened to choose a people for his name from the Gentiles. The words of the prophets are in agreement with this, as it is written:

‘After this I will return and rebuild David’s fallen tent.
Its ruins I will rebuild, and I will restore it,

That the rest of mankind may seek the Lord,
Even all the Gentiles who bear my name,
Says the Lord, who does these things,

Things known from long ago.

“It is my judgment, therefore, that we should not make it difficult for the Gentiles who are turning to God. Instead
we should write to them, telling them to abstain from food polluted by
idols, from sexual immorality, from the meat of strangled animals and
from blood. For the law of Moses has been preached in every city from the earliest times and is read in the synagogues on every Sabbath.”

The Council’s Letter to Gentile Believers

Then the apostles and elders, with the
whole church, decided to choose some of their own men and send them to
Antioch with Paul and Barnabas. They chose Judas (called Barsabbas) and
Silas, men who were leaders among the believers. With them they sent the following letter:

The apostles and elders, your brothers,

To the Gentile believers in Antioch, Syria and Cilicia:

Greetings.
We have heard that some went out from us without our authorization and disturbed you, troubling your minds by what they said. So we all agreed to choose some men and send them to you with our dear friends Barnabas and Paul— men who have risked their lives for the name of our Lord Jesus Christ. Therefore we are sending Judas and Silas to confirm by word of mouth what we are writing. It seemed good to the Holy Spirit and to us not to burden you with anything beyond the following requirements: You
are to abstain from food sacrificed to idols, from blood, from the meat
of strangled animals and from sexual immorality. You will do well to
avoid these things.
Farewell.
So the men were sent off and went down to Antioch, where they gathered the church together and delivered the letter. The people read it and were glad for its encouraging message. Judas and Silas, who themselves were prophets, said much to encourage and strengthen the believers. After
spending some time there, they were sent off by the believers with the
blessing of peace to return to those who had sent them. But Paul and Barnabas remained in Antioch, where they and many others taught and preached the word of the Lord.

The fact that Jesus Christ did not abolish the Law says nothing about
its continued inapplicability to those who are not Jews.  In fact, to
claim it now applies to non-Jews when it did not before on the basis of
Matthew 5:17-20 is clearly self-contradictory, for the obvious reason
that making it applicable to people to whom it did not previously apply
would be changing the letter of it.  Note particularly how Jesus states
even those who “sets
aside one of the least of these commands and teaches others
accordingly” will still nevertheless be part of the kingdom of heaven.