Exodus 19:13, 16

no hand shall touch him, but he shall surely be stoned, or shot through; whether it be beast or man, he shall not live: when the trumpet soundeth long, they shall come up to the mount.

And it came to pass on the third day, when it was morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of a trumpet exceeding loud; and all the people that were in the camp trembled.