(Rabbi Kalonymus Kalman HaLevi Epstein, Poland, 1753-1825)
The Eternal said to Moses, "Behold, I will come to you in a thick cloud, in order that the people will hear when I speak with you [and so they will then trust you.] And Moses reported the words of the people to the Eternal." (Exodus 19:9)
Rashi, of blessed memory, explains that what, "Moses reported," was their response. He said: "I heard from them that what they want is to hear from You directly. For one who hears from a messenger is not like one who hears from the mouth of the King. We want to see our King!"
[Later we read] "And all the people saw the sounds... And they said to Moses, you speak to us, and we will hear, but do not let God speak to us." (Exodus 20:15-16)
And so, when the Blessed One said to Moses, may he rest in peace, "Behold, I will come to you i-n a t-h-i-c-k c-l-o-u-d," this is the numerical value of: 'i-n a h-i-n-t.'
"...in order that the people will hear," meaning that there is the level of 'Hearing,' and then there is a higher level, which is 'Seeing.' And see how the Blessed One said to Moses that God would come at the level of H-e-a-r-i-n-g, which was enough for them, given that their stage of development had only gotten them to the level of Hearing.
"I will come to you i-n a t-h-i-c-k c-l-o-u-d", which has the numerical value of
'i-n a h-i-n-t.' That is, in all the hints of the Torah. But they replied, "We want to see our King!" That is, to come to the level of seeing.
And then, when they did see - as it is written, "and all the people saw the sounds" - Rashi explains that "they saw what is normally heard."
And then, "when the people saw, they fell back," and they asked Our Teacher Moses, "You speak with us, and we will hear [but do not let God speak to us, lest we die.]" For they had only reached the level of Hearing, which is why it had been put to them from the start: "Behold, I will come to you in a thick cloud, in order that the people will hear when I speak with you."