Exodus 19:14-16

Moses went down the mountain to the people and prepared them for the holy meeting. They gave their clothes a good scrubbing. Then he addressed the people: “Be ready in three days. Don’t sleep with a woman.” On the third day at daybreak, there were loud claps of thunder, flashes of lightning, a thick cloud covering the mountain, and an ear-piercing trumpet blast. Everyone in the camp shuddered in fear.