Exodus 19:15-17 New International Version - UK (NIVUK)
15 Then he said to the people, ‘Prepare yourselves for the third day. Abstain from sexual relations.’
16 On the morning of the third day there was thunder and lightning, with a thick cloud over the mountain, and a very loud trumpet blast. Everyone in the camp trembled. 17 Then Moses led the people out of the camp to meet with God, and they stood at the foot of the mountain.