Matthew 12:38-39

Then some of the scribes and Pharisees said to Him, “Teacher, we want to see a sign (attesting miracle) from You [proving that You are what You claim to be].” But He replied and said to them, “An evil and adulterous generation [that is morally unfaithful to God] craves and demands a [miraculous] sign; but no sign will be given to it except the sign of the prophet Jonah; [Luke 11:29-32]