זוהר שמות — דף רלא ע”א

All those who converted afterward did so after seeing the miracles that the Holy One blessed be He performed for Jonah at sea. They saw him fall into the sea and a great fish rise and swallow him before them. That generation was destined to be righteous in the future, and they converted because they saw the heavenly Name sanctified at sea. Jonah ascended to dry land and prophesied about Nineveh, and the repentance of Nineveh preceded the repentance of Nineveh's inhabitants.