Exodus 19:18

18 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, and the whole mountaina trembled violently.

Read Exodus 19:18 Using Other Translations

And mount Sinai was altogether on a smoke, because the LORD descended upon it in fire: and the smoke thereof ascended as the smoke of a furnace, and the whole mount quaked greatly.
Now Mount Sinai was wrapped in smoke because the LORD had descended on it in fire. The smoke of it went up like the smoke of a kiln, and the whole mountain trembled greatly.
All of Mount Sinai was covered with smoke because the LORD had descended on it in the form of fire. The smoke billowed into the sky like smoke from a brick kiln, and the whole mountain shook violently.