Дварим 5:4 Комментарий: Rashi, Sforno, Rabbeinu Bahya & Siftei Chakhamim

פנים בפנים FACE TO FACE — R. Berechia said: Thus did Moses, in effect, say: Do not think that I am misleading you with something which does not exist at all, as an agent does acting between the vendor and the purchaser; behold, the seller Himself is speaking to you (God who transmitted the Torah to you) (cf. Pesikta Rabbati 21: Pesachim Rabbah פ' י' הדברות קמייתא‎).

פנים בפנים, not in a nocturnal vision when you were asleep.