Why the silence of God?

Matthew 12.38-40

Then some of the scribes and Pharisees answered, saying, “Teacher, we want to see a sign from You.” But He answered and said to them, “An evil and adulterous generation seeks after a sign, and no sign will be given to it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth.