The mountain trembled because God Himself had come down upon it. The Targum Pseudo-Jonathan renders the moment with startling directness: the Lord revealed Himself on Mount Sinai, upon the very summit of the mountain, and from that peak He called to Moses. And Moses went up (Exodus 19:20).
Notice what the Aramaic Targum does here. The Hebrew simply says the Lord descended. The Targumist insists the Lord revealed Himself — because God does not physically move from place to place. What descends on Sinai is the Shekinah, the indwelling Presence, appearing in a form the people can bear to witness without being undone.
And where does the Presence settle? Not halfway up the mountain. Not on the slopes. Upon the summit. The highest place, the place closest to heaven, the place no Israelite is permitted to touch. There God waits, and from that unreachable height a voice goes out calling the name of one man.
Moses climbs alone. Every step upward is a step further from the camp and closer to the fire. The Targum leaves the ascent unadorned — no drama, no delay. Moses went up. When God calls, a prophet answers with his feet.
The takeaway: sanctity does not come down to us where we are comfortable. It waits at the summit, and the work of a holy life is the climb.