Exodus 19:16
16 On the morning of the kthird day there were mthunders and lightnings and na thick cloud on the mountain and a very loud otrumpet blast, so that all the people in the camp ptrembled.
Exodus 20:18
18 Now when all the people saw wthe thunder and the flashes of lightning and the sound of the trumpet and the mountain smoking, the people were afraid1 and trembled, and they stood far off