When a prophet speaks in the name of the LORD and the message does not come to pass or come true, that is a message the LORD has not spoken. The prophet has spoken presumptuously. Do not be afraid of him.
Jewish Publication Society of America Version (JPS1917) - Deuteronomy 18:22 >When a prophet speaketh in the name of the LORD, if the thing follow not, nor come to pass, that is the thing which the LORD hath not spoken; the prophet hath spoken it presumptuously, thou shalt not be afraid of him.