I do not accept human praise/testimony. Where do we get the strength to continue doing good even in the face of opposition? Where does our will power come from? Faced with opposition from a section of the religious leaders, Jesus refuses to rely on human praise/testimony to back him up. He refuses to bow to their request on two grounds: he knows that human testimony is short lived because of their lack of faith. John testified to Jesus’ authenticity and even though for a little while the people rejoiced, it did not last long. Even Moses and the other prophets foretold of his coming (cf. Deut 18:15: God will raise a prophet like me; you will listen to him…), yet they have still refused to believe in, and listen to him. Even if others were to testify now on his behalf, it would serve no good.
Secondly, Jesus tells the people that if his actions and words are about the truth, then that truth will become self-evident. He doesn’t need to be backed up by what the people say. He will let his actions speak on his behalf. When pagans and non-believers will come to believe in Israel’s God, then they will clearly come to see that Jesus is truly from the Father and that he is doing God’s will. It is in the knowledge that he is doing God’s will that Jesus will rely. His life and ministry will be his testimony.