'Cloud' in the Bible

and Yahweh said to Moses, "Tell Aaron your brother, not to come at all times into the Most Holy Place within the veil, before the mercy seat which is on the ark; lest he die: for I will appear in the cloud on the mercy seat.

and he shall put the incense on the fire before Yahweh, that the cloud of the incense may cover the mercy seat that is on the testimony, so that he will not die.