הֶֽ֭הָרִים רָקְד֣וּ כְאֵילִ֑ים גְּ֝בָע֗וֹת כִּבְנֵי־צֹֽאן׃
les montagnes bondirent comme des béliers, les collines comme des agneaux.
Midrash BeChiddush
הֶ֭הָרִים רָקְד֣וּ כְאֵילִ֑ים “The mountains skipped like rams.” (Ps. 114:4) This statement is made about the two mountains which were found at the Arnon River crossing at which the Amorites hid and they traveled from one site to the other like the rams which would butt one another. 310See Numbers 21:24 Arnon is first mentioned in Num. 21:24 as the border between Moab and the Amorites. "The valleys of Arnon" in the next verse undoubtedly indicate the numerous wadies contributory to the mainstream. https://bibleatlas.org/arnon.htm
Midrash BeChiddush
גְּ֝בָע֗וֹת כִּבְנֵי־צֹֽאן “The hills like sheep.” (Ps. 114:4) It is the nature of sheep to hop about and run a little and then to return to their mother. So too happened with the mountains and the hills which were happy when Israel entered the land of Canaan, as is written, “Before you, mount and hill shall shout aloud,” (Is. 55:12)
Tur HaArokh
וכל העם רואים את הקולות, “The whole nation was able to see the sounds, etc.” This is not the only time that the term “seeing” is used instead of “hearing.” Another such instance is found in Genesis 42,1 where Yaakov is described as “seeing” that there was food for sale in Egypt, a distance of hundreds of kilometers from where he was at the time. What was meant is that he had heard about it, from returning travelers. Our sages understand the verse literally, i.e. that during these exalted moments the people actually saw the sounds, the words. Nachmanides writes that our verse does not describe what the Israelites had seen during the revelation, but what occurred later, and that this is what Moses referred to in Deut.5,20 ותקרבון אלי וגו', “you approached me, etc.” They told Moses at that time that they could no longer endure the voice of G’d and were afraid to die unless Moses from then on would act as their interpreter. Personally, Nachmanides’ opinion is not acceptable to me, considering the fact that the Torah quotes the Israelites as saying words of a similar nature already in our paragraph immediately after the conclusion of the Decalogue. At that point nothing was said about the Israelites being afraid to die as a result of the overwhelming impact of what they had experienced. Furthermore, Moses is already telling the people: “אל תיראו, “do not be afraid (that you will die).” G’d had already commented that the people had done well in requesting that Moses be their interpreter of G’d’s words. (Deut. 5,25) I believe that the chronological sequence of what is reported in these paragraphs is as follows: the paragraph commencing with the words וכל העם (20,15) reports something which had preceded the actual giving of the Ten Commandments. As an introductory preamble, the Torah, i.e. Moses relates all the instructions he had received concerning the fencing off of the Mountain, followed by the proclamation of the Ten Commandments. Now Moses reviews what the Israelites had been saying to him in the course of this whole procedure, reminding them that from the moment they saw thunder and lightning they had trembled, retreated backwards, and taken up a position quite some distance from the bottom of the Mountain, way beyond the security fence Moses had erected. The secret to understanding all this lies in the fact that from early morning on the day of the revelation there were continuous explosion-like sounds of thunder, tremendous flashes of lightning, all of which preceded the manifestation of G’d’s presence. The people reasoned, understandably, that the intensity of these phenomena was likely to increase still further once the Shechinah began to manifest itself. Moses, in order to demonstrate to them that they had nothing to fear, led them closer to the bottom of the Mountain, a location from which the descent of the Shechinah to the top of the Mountain could be observed as a spectacle resembling the smoke arising from a crucible (19,18) all the way to heaven. The very Mountain started trembling, as if they were experiencing a major earthquake. David, in Psalms 114,4 describes the mountains of the Sinai range as dancing like rams. Seeing that, as reported, the sound of the shofar instead of receding, continued to become ever louder, the people reacted accordingly. The description by David in Psalms is not allegorical, just as the description of the sea fleeing from G’d at the time He split the Sea of Reeds, (Psalms 114,3) is not allegorical, but is a factual description of what had occurred. At that point, the people turned to Moses in awe, begging him to become their interpreter. They were willing or even eager to skip the experience of hearing the Lord address them directly. They had not even wanted to respond to Moses’ encouraging overtures to approach the Mountain somewhat closer to the edge of the fence. They observed Moses approach the thick cloud within which the presence of the Shechinah was concealed. He did however, not enter it. At that point, G’d began to recite the Decalogue. The Torah, at this juncture does not report at all what the elders had been saying to Moses, i.e. the recollection of events as presented in Deuteronomy to the new generation, shortly before he himself was to die. At this juncture the Torah’s major concern was to begin to elaborate on all the commandments, primarily the ones dealing with inter-personal relations that are set out in the portion called משפטים in chapters 21-23. In the Book of Deuteronomy, however, Moses does relate that all the leaders of the people after the revelation approached him, expressing their profound fear that if they were to be exposed to more mind-boggling experiences like these they would not be able to endure this. The reason they approached Moses at that time was that they thought G’d would address all the Commandments to them in the manner experienced at the Mountain. They therefore gave Moses their leader carte blanche to accept all these Commandments on their behalf committing themselves to observe any and all of these Commandments they had not been informed of as yet. G’d agreed with the feelings the Israelites had expressed. It had been His intent all along that the people would only hear the Decalogue from His mouth directly.