When a prophet speaks in the name of the LORD, if the thing does not come about or come true, that is the thing which the LORD has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him (Deuteronomy 18:22).
And Jonah began to enter into the city a day’s journey, and he cried, and said, Yet forty days, and Nineveh shall be overthrown (Jonah 3:4).
So Jonah was a false prophet. Yet in the Bible...
“So Jonah was a false prophet. Yet in the Bible...”
No, Jonah spoke just the words the Lord gave him, however the Lord did not give him the whole message. That is what a prophet does, speaks just the words the Lord gives.
“Leave at once for the important city, Nineveh. Announce to the people that I can no longer overlook the wicked things they have done.”
“Leave at once for the important city, Nineveh. Announce to the people the message I have given you.”