Tafsiran Ulangan 5:4: Rashi, Ibn Ezra, Sforno & Rabbeinu Bahya

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).

face to face i.e., without an intermediary. When someone’s voice can be heard directly, it is called “face to face”, even if his face cannot be seen.

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