Charles Ellicott Commentary Exodus 33:1-6

"And Jehovah spake unto Moses, Depart, go up hence, thou and the people that thou hast brought up out of the land of Egypt, unto the land of which I sware unto Abraham, to Isaac, and to Jacob, saying, Unto thy seed will I give it: and I will send an angel before thee; and I will drive out the Canaanite, the Amorite, and the Hittite, and the Perizzite, the Hivite, and the Jebusite: unto a land flowing with milk and honey: for I will not go up in the midst of thee, for thou art a stiffnecked people, lest I consume thee in the way. And when the people heard these evil tidings, they mourned: and no man did put on him his ornaments. And Jehovah said unto Moses, Say unto the children of Israel, Ye are a stiffnecked people; if I go up into the midst of thee for one moment, I shall consume thee: therefore now put off thy ornaments from thee, that I may know what to do unto thee. And the children of Israel stripped themselves of their ornaments from mount Horeb onward." — Exodus 33:1-6 (ASV)

If God consented at all to renew His covenant with the people, after they had so flagrantly broken it, the terms on which He would renew it were, in strict justice, purely optional. In the “Book of the Covenant” He had promised to go up with them by an Angel, in whom was His Name (Exodus 23:20–23): that is, by His Son, the Second Person in the Holy Trinity.

He now, to mark His displeasure, withdrew this promise, and substituted for the Divine presence that of a mere angel: I will send an angel before you (Exodus 33:2); I will not go up in the midst of you (Exodus 33:3).

Dimly the people felt the importance of the change—the vast difference between the angelic and the Divine—and mourned their loss (Exodus 33:4). They mourned with some touch of real godly sorrow and, as was the custom of Eastern peoples in mourning (Terence, Heauton Timorumenos 2.3.47; Herodian 4.2, etc.), put off their ornaments.