John 2:18
Then the Jews addressed him and said, "What sign have you to show us, for acting in this way?"
John 6:30
Then they said to him, "Then what sign do you show for us to see and so come to believe you? What work are you doing?
Matthew 12:39
But he answered, "Only a wicked and faithless age insists upon a sign, and no sign will be given it but the sign of the prophet Jonah.
John 10:38
But if I am doing them, then even if you will not believe me, believe the things I do, in order that you may realize and learn that the Father is in union with me, and I am in union with the Father."