John 5:36

But the witness that I have is greater than that of John; for the works the Father hath given me to accomplish, the very works that I do bear witness of me, that the Father hath sent me.

John performed no miracle; and there was a strong opinion within the very group Jesus was addressing, an opinion stated by Nicodemus that "We know that no man can do the signs thou doest, except God be with him" (John 3:2). Also, God had spoken out of heaven in broad open daylight in the presence of thousands saying, "This is my beloved Son." The works of Jesus, empowered by God, were the most fantastically powerful deeds ever done on earth, nor has there ever been any successful denial that such world-shaking signs were literally and actually done by him. Feeding a multitude, walking on the sea, raising the dead again, and again, and again - all men, like Nicodemus, should know that only God could have done such things.