Charles Ellicott Commentary Exodus 34:5

"And Jehovah descended in the cloud, and stood with him there, and proclaimed the name of Jehovah." — Exodus 34:5 (ASV)

The Lord descended in the cloud. —When Moses ceased to commune with God, the cloud moved from the door of the “Tent of Meeting,” and, as it would seem, disappeared. When Moses reached the summit of Sinai, it once more became visible, descended on the spot where Moses was, and stood with him there.

And proclaimed the name of the Lord. —Compare Exodus 33:19; and for the terms of the proclamation see Exodus 34:6-7.