Galatians 1:9

As we have before spoken, and I now repeat it again, If any man preach a gospel different from that ye have received, let him be anathema.

Romans 16:17

Now I beseech you, brethren, keep a sharp eye over those who cause divisions and offences contrary to the doctrine ye have learned, and turn away from them.

2 Corinthians 1:17

Such then being my intention, did I indeed change it with levity? or the things which I purpose, do I purpose after the flesh, that with me there should be yea, yea, and nay, nay?

2 Corinthians 13:1-2

THIS third time I am coming to you: by the mouth of two or three witnesses shall every charge be established.

Philippians 3:1

MOREOVER, brethren, rejoice in the Lord. To write the same things to you, to me indeed is not irksome, but is safe for you.

Philippians 4:4

Rejoice in the Lord always; again I say, Rejoice.

Revelation 22:18-19

For I testify to every one who heareth the words of the prophecy of this book, If any man add to these things, God will lay upon him the plagues that are written in this book:

Treasury of Scripture Knowledge

Summary

As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed.

General references

Bible References

So

2 Corinthians 1:17
Such then being my intention, did I indeed change it with levity? or the things which I purpose, do I purpose after the flesh, that with me there should be yea, yea, and nay, nay?
2 Corinthians 13:1
THIS third time I am coming to you: by the mouth of two or three witnesses shall every charge be established.
Philippians 3:1
MOREOVER, brethren, rejoice in the Lord. To write the same things to you, to me indeed is not irksome, but is safe for you.
Philippians 4:4
Rejoice in the Lord always; again I say, Rejoice.

Than

Revelation 22:18
For I testify to every one who heareth the words of the prophecy of this book, If any man add to these things, God will lay upon him the plagues that are written in this book:

General references

1 Corinthians 3:11
For other foundation can no man lay than that is laid, which is Jesus the Messiah.