Let's get this straight. You don't believe it's a prophecy in John 2:19, but it's clearly a prophecy in Matthew 12:39, 40. Compare it to John 2:19. It's a prophecy. And notice he said he will be three day and night in the heart of the earth, not paradise.
Matthew 12
39But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
40For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
John 2
19Jesus answered and said unto them, Destroy this temple, and in three days I will raise it up.