(9) And G-d said unto Moses: ‘Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and may also believe thee for ever.’ And Moses told the words of the people unto the G-d.

(12) And thou shalt set bounds unto the people round about, saying: Take heed to yourselves, that ye go not up into the mount, or touch the border of it; whosoever toucheth the mount shall be surely put to death; (13) no hand shall touch him, but he shall surely be stoned, or shot through; whether it be beast or man, it shall not live; when the ram’s horn soundeth long, they shall come up to the mount.’

I have an answer...I heard from them that they want to hear {directly} from You! "one can't compare hearing from a messenger to hearing from the King Himself...we want to see our King"

(20) And it came to pass, when ye heard the voice out of the midst of the darkness, while the mountain did burn with fire, that ye came near unto me, even all the heads of your tribes, and your elders; (21) and ye said: ‘Behold, the LORD our God hath shown us His glory and His greatness, and we have heard His voice out of the midst of the fire; we have seen this day that God doth speak with man, and he liveth. (22) Now therefore why should we die? for this great fire will consume us; if we hear the voice of the LORD our God any more, then we shall die. (23) For who is there of all flesh, that hath heard the voice of the living God speaking out of the midst of the fire, as we have, and lived? (24) Go thou near, and hear all that the LORD our God may say; and thou shalt speak unto us all that the LORD our God may speak unto thee; and we will hear it and do it.’ (25) And the LORD heard the voice of your words, when ye spoke unto me; and the LORD said unto me: ‘I have heard the voice of the words of this people, which they have spoken unto thee; they have well said all that they have spoken.

The people shall hear when I speak with you—and they themselves will become prophets, when I speak—they will not simply believe on the authority of others, as it is said, “God said to me: Gather the people for Me, so that I may have them hear My words, in order that they may learn to fear Me all the days.” (Deut 4:10) Moreover, they will believe in you eternally, through all generations: And if there should arise in their midst a prophet or a dreamer of dreams, who opposes your words, they will repudiate him immediately. For they have already seen with their eyes and heard with their ears that you have reached the highest level of prophecy. For that reason, God said, “The people will hear when I speak with you:” they will hear My words from out of the fire, and they will know that I, God, am speaking with you, and they will believe My words and also believe in you for ever. That is what the people say: “This day we have seen that God will speak with a human being and he may live” (Deut 5:20)—meaning, “The possibility of hearing God speak has been realized by us, in the seeing of our eyes, as God desired.” So, from now on, “you (Moses) go close to God”—for we know that you have attained greatness—“and listen to all that God, our God says, and we will hear from your mouth, and obey”—for your prophecy has now been validated, that it is the highest of all.

R. Levi said: Two things Israel requested from God—to see His glory and to hear His voice. And they did see His glory and hear His voice, as it is said, “See, God our God has shown us His glory and His greatness,” and it is written, “His voice we have heard from out of the fire.” (Deut 5:21) But they did not have strength to stand, for when they came to Sinai and He was revealed to them, they fainted (lit. their souls flew away), when He spoke with them, as it is said, “I was faint (lit. My soul left me) when he spoke” (Song of Songs 5:6). But the Torah asked God for mercy: “Does a king marry off his daughter and kill his household? The whole world is rejoicing, and Your children die!” Immediately, they revived, as it is written, “God’s Torah is perfect, restoring life” (Ps 19:8).16

“I am God your God …” (20:2). It is written, “Has a people ever heard the voice of God …?” (Deut 4:33). Heretics asked R. Simlai: “Are there many gods in the world?” He asked, “Why?” They answered: “Because it is written, ‘Has a people heard the voice of elohim,’ in the plural!” He told them, “But it does not say, ‘God speaking—medabrim’—in the plural, but medaber—in the singular!” His students then said to him: “You have fobbed them off with a reed (i.e., easily): what do you answer us?” So R. Levi explained again: “Has a people ever heard the voice of God …?” If it had said, “The voice of God is in His strength,” the world would not have been able to stand. But the text says: “The voice of God is in strength” (Ps 29:4)—that is, according to the strength of each individual—young men, according to their strength, and the old, according to their strength, and children, according to their strength. God said to Israel: “Just because you heard many voices, do not think that there are many gods in heaven, but be aware that I am God your God, as it is said, ‘I am God your God …’ ”