Guide for the Perplexed, by Moses Maimonides, Friedländer tr. [1904], at sacred-texts.com
IT is clear to me that what Moses experienced at the revelation on Mount Sinai was different from that which was experienced by all the other Israelites, for Moses alone was addressed by God, and for this reason the second person singular is used in the Ten Commandments; Moses then went down to the foot of the mount and told his fellow-men what he had heard. Comp., "I stood between the Lord and you at that time to tell you the word of the Lord" (Deut. v. 5). Again, "Moses spake, and God answered him with a loud voice" (Exod. xix. 19). In the Mechilta our Sages say distinctly that he brought to them every word as he had heard it. Furthermore, the words, "In order that the people hear when I speak with thee" (Exod. xix. 9), show that God spoke to Moses, and the people only heard the mighty sound, not distinct words. It is to the perception of this mighty sound that Scripture
refers in the passage, "When ye hear the sound" (Deut. v. 20); again it is stated, "You heard a sound of words" (ibid. iv. 12), and it is not said "You heard words"; and even where the hearing of the words is mentioned, only the perception of the sound is meant. It was only Moses that heard the words, and he reported them to the people. This is apparent from Scripture, and from the utterances of our Sages in general. There is, however, an opinion of our Sages frequently expressed in the Midrashim, and found also in the Talmud, to this effect: The Israelites heard the first and the second commandments from God, i.e., they learnt the truth of the principles contained in these two commandments in the same manner as Moses, and not through Moses. For these two principles, the existence of God and His Unity, can be arrived at by means of reasoning, and whatever can be established by proof is known by the prophet in the same way as by any other person; he has no advantage in this respect. These two principles were not known through prophecy alone. Comp., "Thou hast been shown to know that," etc. (Deut. iv. 34). But the rest of the commandments are of an ethical and authoritative character, and do not contain [truths] perceived by the intellect. Notwithstanding all that has been said by our Sages on this subject, we infer from Scripture as well as from the words of our Sages, that the Israelites heard on that occasion a certain sound which Moses understood to proclaim the first two commandments, and through Moses all other Israelites learnt them when he in intelligible sounds repeated them to the people. Our Sages mention this view, and support it by the verse, "God hath spoken once; twice have I heard this" (Ps. lxii. 11). They state distinctly, in the beginning of Midrash Ḥazita, that the Israelites did not hear any other command directly from God; comp. "A loud voice, and it was not heard again" (Deut. v. 19). It was after this first sound was heard that the people were seized with the fear and terror described in Scripture, and that they said, "Behold the Lord our God has shown us, etc., and now why shall we die, etc. Come thou near," etc. Then Moses, the most distinguished of all mankind, came the second time, received successively the other commandments, and came down to the foot of the mountain to proclaim them to the people, whilst the mighty phenomena continued; they saw the fire, they heard the sounds, which were those of thunder and lightning during a storm, and the loud sound of the shofar: and all that is said of the many sounds heard at that time, e.g., in the verse, "and all the people perceived the sounds," etc., refers to the sound of the shofar, thunder, and similar sounds. But the voice of the Lord, that is, the voice created for that purpose, which was understood to include the diverse commandments, was only heard once, as is declared in the Law, and has been clearly stated by our Sages in the places which I have indicated to you. When the people heard this voice their soul left them; and in this voice they perceived the first two commandments. It must, however, be noticed that the people did not understand the voice in the same degree as Moses did. I will point out to you this important fact, and show you that it was a matter of tradition with the nation, and well known by our Sages. For, as a rule, Onkelos renders the word va-yedabber by u-mallel ("and God spake"); this is also the case with this word in the beginning of the twentieth chapter of Exodus, but the words ve-al yedabber immanu elohim, "let not God speak to us"
[paragraph continues] (Exod. xx. 19), addressed by the people to Moses, is rendered vela yitmallel immanu min kodam adonai ("Let not aught be spoken to us by the Lord"). Onkelos makes thus the same distinction which we made. You know that according to the Talmud Onkelos received all these excellent interpretations directly from R. Eliezer and R. Joshua, the wisest men in Israel. Note it, and remember it, for it is impossible for any person to expound the revelation on Mount Sinai more fully than our Sages have done, since it is one of the secrets of the Law. It is very difficult to have a true conception of the events, for there has never been before, nor will there ever be again, anything like it. Note it.