'Cloud' in the Bible

and Jehovah said unto Moses, Speak unto Aaron thy brother, that he come not at all times into the holy place within the veil, before the mercy-seat which is upon the ark; that he die not: for I will appear in the cloud upon the mercy-seat.

and he shall put the incense upon the fire before Jehovah, that the cloud of the incense may cover the mercy-seat that is upon the testimony, that he die not: