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. Then Moses led the people out of the camp to meet with God, and they stood at the foot of the mountain. Mount Sinai was covered with smoke, because the Lord descended on it in fire. The smoke billowed up from it like smoke from a furnace, the whole mountain trembled violently, and the sound of the trumpet grew louder and louder. Then Moses spoke and the voice of God answered him (Exodus 19:16-19 NIV).