Bible Dictionary
BACK, BACK PARTS
“Back” or “back parts” may refer to the far side or rear of a place. When God’s “back” is mentioned, the expression is an anthropomorphic way of describing a limited glimpse or afterglow of His divine glory.
Biblical Usage
The expression describes Moses seeing God’s “back,” understood as the afterglow or faint reflection of God’s essential glory. Other biblical uses refer to a wilderness area, geographical direction, and writing on the reverse or back portion of a roll.