What is the apple of God's eye?

[TonyChanYT]

Let's see the parallelism of Psalm 17:8

Keep me as the apple of your eye;
hide me in the shadow of your wings

It's a symbol of protection from God.

as the apple
כְּאִישׁ֣וֹן (kə·’î·šō·wn)
Preposition-k | Noun - masculine singular construct
Strong's Hebrew 380: The little man of the eye, the pupil, ball, the middle

Barnes depicts it nicely:

Keep me as the apple of the eye - Preserve me; guard me; defend me, as one defends that which is to him most precious and valuable. ...
The literal translation would be, "Keep me as the little man - the daughter of the eye." ...
the apple or pupil of the eye, "in which, as in a mirror, a person sees his own image reflected in miniature." ...
The idea here is, that the little image is the "child" of the eye; that it has its birth or origin there. The prayer of the psalmist here is, that God would guard him, as one guards his sight - an object so dear and valuable to him.

Rashi:

[as the apple] Heb. (כאישון). That is the pupil (lit. the black) of the eye, on which the vision depends. Because it is black, it is called אישון, an expression of darkness, and the Holy One, blessed be He, prepared a guard for it, viz. the eyelids, which constantly cover it.

 

[hawkman]

What did God say should be the apple of our eye ?