Galatians 5:10

“Since we have heard that some of us, to whom we gave no instruction, have gone out and disturbed you with their words, unsettling your souls,

And this is the very thing I wrote you, so that when I came, I would not have sorrow from those who ought to make me rejoice; having confidence in you all that my joy would be the joy of you all.

which is really not another, only there are some who are disturbing you and want to distort the gospel of Christ.

I wish that those who are upsetting you would even mutilate themselves.

Let us therefore, as many as are perfect, think this way; and if in anything you think differently, God will reveal that also to you.

The one who believes in the Son of God has this witness in himself. The one who does not believe God has made Him a liar, because he has not believed in the witness which God has borne witness about His Son.