John 2:18
Upon this the Jews asked Jesus: "What sign are you going to show us, since you act in this way?"
John 6:30
"What sign, then," they asked, "are you giving, which we may see, and so believe you? What is the work that you are doing?
Matthew 12:39
"It is a wicked and unfaithful generation," answered Jesus, "that is asking for a sign, and no sign shall be given it except the sign of the Prophet Jonah.
John 10:38
If I am doing it, even though you do not believe me, believe what that work shows; so that you may understand, and understand more and more clearly, that the Father is in union with me, and I with the Father."