וְכִ֥י תֹאמַ֖ר בִּלְבָבֶ֑ךָ אֵיכָה֙ נֵדַ֣ע אֶת־הַדָּבָ֔ר אֲשֶׁ֥ר לֹא־דִבְּר֖וֹ יְהוָֽה׃
And if thou say in thy heart: ‘How shall we know the word which the LORD hath not spoken?’
Targum Jonathan on Deuteronomy
And if thou shalt say in your thoughts, How shall we know the word which the Lord hath not spoken?