Yahweh prepared a great fish to swallow up Jonah, and Jonah was in the belly of the fish three days and three nights.
The three-day time was significant also because Jonah’s deliverance became a precursor of an even greater salvation that took three days and nights to accomplish (Matthew 12:40). God restored Jonah to life so he would be God’s instrument in providing salvation to a large Gentile (and indirectly Jewish) population under God’s judgment for their sins. He raised Jesus to life so He would be God’s instrument in providing salvation for an even larger population of Gentiles and Jews under God’s judgment for their sins.