Jonah spent three days in the deep and then preached overthrow to a city that actually repented. Jesus claims that pattern.
The sign is the prophet’s descent and emergence, then a word of judgment. Nineveh heard. “This generation” mostly did not.
Matthew 12 and 16 refuse extra credentials. Resurrection is the credential.
Jonah’s city turned. Jerusalem, with a greater than Jonah, doubled down until the overthrow arrived.
The sign has been given. New Creation faith does not wait for a different one.