(Ibid. 20:15) "And all the people saw the sounds and the lightnings": They saw what was visible and heard what was audible. These are the words of R. Yishmael. R. Akiva says: They saw and heard what was audible. There was nothing that left the mouth of the Omnipotent which was not inscribed on the tablets, as it is written (Psalms 29:7) "The voice of the L–rd hews (with) flames of fire."