Thought from Today's Old Testament Passage: And the Lord said, "Here is a place by Me, and you shall stand on the rock. So it shall be, while My glory passes by, that I will put you in the cleft of the rock, and will cover you with My hand while I pass by. Then I will take away My hand, and you shall see My back; but My face shall not be seen." Exodus 33:21-23
God placed Moses in a cleft in the rock, apparently a cavelike crevice, and he then caused his glory to pass by. The glory of God refers first and foremost to the sheer weight or the reality of his presence. The presence of God would come near Moses in spatial terms.
But Moses would not be able to endure the spectacular purity, luminosity and reality of staring at the raw glory of God himself. Instead, God would protect Moses from accidental (and apparently, fatal) sight of that glory. Therefore, in a striking anthropomorphism (a description of the reality of God in terms or analogies understandable to mortals), God would protect Moses from the full effects of looking directly at the glory of God by placing his hand over Moses' face until all God's glory had passed by.
That this is a figure of speech is clear from the double effect of God passing by and while simultaneously protecting Moses with the divine "hand." Only after his glory, or presence, had passed by would God remove his gracious, protecting "hand." Then Moses would view what God had permitted.
But what was left for Moses to see? The translators say God's back. But since God is spirit (Is 31:3; Jn 4:24) and formless, what would this refer to? The word back can as easily be rendered the afte reffects of the glory that had passed by.
This would fit the context as well as the range of meanings for the Hebrew word used. Moses did not see the glory of God directly, but once it had gone past, God did allow him to view the results, the afterglow, that his presence had produced.
Walter C. Kaiser, Jr., Hard Sayings of the Old Testament (Downers Grove, IL: InterVarsity Press, 1988), pp. 83-84