No Other Gospel
I am astonished that you are so quickly deserting him who called you in the grace of Christ and are turning to a different gospel— not that there is another one, but there are some who trouble you and want to distort the gospel of Christ. But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed. As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed.
For am I now seeking the approval of man, or of God? Or am I trying to please man? If I were still trying to please man, I would not be a servant of Christ.
Galatians 1 (ESV)