In Context

18 a prophet I raise up to them, out of the midst of their brethren, like to thee; and I have given my words in his mouth, and he hath spoken unto them all that which I command him;

19 and it hath been — the man who doth not hearken unto My words which he doth speak in My name, I require it of him.

20 Only, the prophet who presumeth to speak a word in My name — that which I have not commanded him to speak — and who speaketh in the name of other gods — even that prophet hath died.

21 And when thou sayest in thy heart, How do we know the word which Jehovah hath not spoken? —

22 that which the prophet speaketh in the name of Jehovah, and the thing is not, and cometh not — it is the word which Jehovah hath not spoken; in presumption hath the prophet spoken it; — thou art not afraid of him.

Deuteronomy 18:21 in Other Translations