81. From the manner in which this incident is described at various places in the Qur'an it is obvious that, at that time, it was quite well known to the Israelites. It is difficult, however, after the Passage of many centuries to be able to speak with certainty about the precise nature of the incident. All we can say is that while the Children of Israel were making their covenant in the shadow of Mount Sinai, they witnessed an awesome phenomenon and felt as if the mountain was about to fall upon them. (Verse 171 of Surah al-A'raf) seems to portray this. See also (n. 132 in that surah.)