John 8:17-18

Therefore Jesus was not really testifying alone. There was a second witness that the law demanded, namely, the Father.

Jesus’ reference to "your law" is unusual since in one sense it was His law. However, Jesus was in the process of setting aside the Law of Moses. The revelation that He brought superseded it, so in another sense it belonged to the Pharisees but not to Him (cf. John 7:19; John 7:51).

"No human witness can authenticate a divine relationship. Jesus therefore appeals to the Father and Himself, and there is no other to whom He can appeal." [Note: Morris, p. 393.]