The verse states that the Israelites “saw the thunder” during the revelation of God at Sinai. The Sages disagree as to the meaning of that phrase, and describe how the Israelites stood ready on the occasion of the giving of the Torah, when they were in a state of total perfection in both mind and body.

“All the people were seeing the thunder and the flames and the blast of the shofar and the mountain smoking” (Exodus 20:15). They were seeing the flames and smoking mountain, which are usually seen, and hearing the thunder and shofar, which are usually heard; this is the statement of Rabbi Yishmael. Rabbi Akiva says: They were seeing and hearing that which is usually only seen – they would see a speech of fire emerging from the mouth of the Almighty and being carved onto the tablets, as it is stated: “The voice of the Lord hews flames of fire” (Psalms 29:7). Rabbi Eliezer says: The verse serves to notify us of the praise of Israel, as when they all stood before Mount Sinai to receive the Torah, it relates that there were no blind people among them, as it is stated: “All the people were seeing” (Exodus 20:15); it relates that there were no mutes among them, as it is stated: “All the people answered together” (19:8); and it teaches that there were no deaf people among them, as it is stated: “Everything that the Lord has spoken we will perform and we will heed” (24:7). From where is it derived that there were no cripples among them? As it is stated: “They stood at the foot of the mountain” (19:17). And the verse teaches that there were no simpletons among them, as it is stated: “You have been shown in order to know” (Deuteronomy 4:35) [indicating that they all had wisdom]. (Mekhilta deRabbi Yishmael, Yitro, Mesekhta deBaĥodesh 9)