God's instruction to Moses at Sinai comes with a precise choreography. "Go down, and then ascend, thou and Aaron with thee; but let not the priests or the people directly come up to gaze before the Lord, lest He slay them" (Exodus 19:24, Targum Pseudo-Jonathan).
The Targum Pseudo-Jonathan catches a difficulty in the Hebrew. The text refers to kohanim — priests — but this is before Aaron's sons have been consecrated, before the Mishkan, before Sinai's tablets are carved. Who are these priests? The Targumist leaves the term, trusting the reader to understand: these are the firstborn, who served in a priestly role before the tribe of Levi was chosen. They wanted to climb. They were hungry for the fire.
But God says no. Only Moses and Aaron. And even they must descend first and re-ascend together — a careful back-and-forth that keeps the boundary intact. The Shekinah on Sinai is not tame. To gaze at it without sanctification is to be consumed.
The word lest He slay them is not a threat but a physics. Holiness unmediated is fatal, the way unshielded sunlight burns. The priests were zealous, and zeal without structure is its own kind of idolatry.
The takeaway: closeness to the Divine is not a reward for enthusiasm; it is a discipline of order.