Then some of the scribes and Pharisees answered him, saying, “Teacher, we wish to see a sign from you.” ³⁹ But he answered them, “An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah. ⁴⁰ For just 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.

(Matthew 12:38-40 -- ESV)