Devarim 18:19-21

Orthodox Jewish Bible

¹⁹ And it shall come to pass, that whosoever will not listen unto My words which he shall speak Bishmi (in My Name), I will require it of him.

²⁰ But the navi, which shall presume to speak a word Bishmi (In My Name), which I have not commanded him to speak, or that shall speak in the shem of elohim acharim, even that navi shall die.

²¹ And if thou say in thine lev, How shall we know the word which Hashem hath not spoken?