Charles Ellicott Commentary Deuteronomy 18:22

"when a prophet speaketh in the name of Jehovah, if the thing follow not, nor come to pass, that is the thing which Jehovah hath not spoken: the prophet hath spoken it presumptuously, thou shalt not be afraid of him." — Deuteronomy 18:22 (ASV)

If the thing follow not, nor come to pass.— This is one form of our Lord’s test for all prophets, “By their fruits (i.e., the ‘results,’ of their teaching, not its first impressions) ye shall know them.”