The Hebrew babah (also bath ayin, 'daughter of the eye') refers to the pupil of the eye. This tender term is used metaphorically to describe something infinitely dear and carefully guarded. To be the babah of God's eye means to be His most treasured possession.
Babah communicates the intensity of divine care. Just as a person instinctively and reflexively protects the pupil of their eye, God protects His people with the same immediacy and ferocity. Deuteronomy 32:10 uses this imagery for God's care over Israel in the wilderness — found in a howling desert waste, He shielded them as the apple of His eye. This intimacy of divine protection is among the most tender metaphors in Scripture.