The Scribes and Pharisees demand of Jesus a sign, not because they want to believe in Him, but to challenge Him and His authority. What greater sign could God have given them than coming to them in the person of His Son? We do not need signs to have faith. Rather we should place our whole confidence in Christ for in Him all the fullness of the Godhead dwells and is given to us each time we receive holy communion.
38 Some of the scribes and Pharisees said to Jesus, “Teacher, we wish to see a sign from you.” 39 He said to them in reply, “An evil and unfaithful generation seeks a sign, but no sign will be given it except the sign of Jonah the prophet. 40 Just as Jonah was in the belly of the whale three days and three nights, so will the Son of Man be in the heart of the earth three days and three nights. 41 At the judgment, the men of Nineveh will arise with this generation and condemn it, because they repented at the preaching of Jonah; and there is something greater than Jonah here. 42 At the judgment the queen of the south will arise with this generation and condemn it, because she came from the ends of the earth to hear the wisdom of Solomon; and there is something greater than Solomon here.”
t h i n k : We do not need signs to have faith.