Specifically;
Matthew 5:17-18
New International Version (NIV)
The Fulfillment of the Law
17 “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. 18
For truly I tell you, until heaven and earth disappear, not the smallest letter, not the least stroke of a pen, will by any means disappear from the Law until everything is accomplished.
That's clear text, not open to interpretation.
Jesus said the Jewish Law is in effect till the end of days. A sin in the Old Testament is a sin in the New Testament. You don't get to pick and choose what actions are sins, only we athiests do.