'Testimony is True' in the Bible

Jesus answered and said unto them, Though I bear witness of myself, my testimony is true: for I know whence I came, and whither I am going; but ye know not whence I come, nor whither I go.

And he that saw it testifieth it, and his testimony is true: and he knoweth that he saith true, that ye may believe.

This is the disciple that testifieth of these things, and that writeth them: and we know that his testimony is true.