2 Corinthians 13:1-3

This is the third time I am coming to you. In the mouth of two or three witnesses shall every word be established.

I told you before, and foretell you, as if I were present, the second time; and being absent now I write to them which heretofore have sinned, and to all other, that, if I come again, I will not spare:

Since ye seek a proof of Christ speaking in me, which to you-ward is not weak, but is mighty in you.