Some of the scribes and Pharisees said to Jesus,
“Teacher, we wish to see a sign from you.”
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.
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.
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.
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.” (Matthew 12:38-42)

The story of Jonah, our reading today, often appears over the remains of someone deceased in the Christian catacombs of early Rome. The whole story is usually there, from Jonah getting thrown off the boat, to being swallowed up by the whale, to Jonah sitting in the shade of the vine. Why?

The early Christians recognized the wisdom in the stories of the Jewish scriptures much more than we do today, I think. They must have seen themselves and their loved ones who passed on as “the men of Nineveh”, people of the great city of Rome, who heard the preaching of Jesus and believed. 

He had the power to bring them life. They believed in the mystery of the One who was three days and three nights in the earth and rose again.

Jonah, the prophet, was their patron saint.