Many of David’s prayers were encompassed in two words: Keep me!
The role of Protector is one of God’s most glorious attributes. He promised Zechariah two forms of protection. First, He promised to be “a wall of fire around Jerusalem” (Zechariah 2:5). Even wild animals fear fire, and God said that He would erect around us a wall of flaming fire that no enemy could penetrate.
God also promised Zechariah that “he that toucheth you toucheth the apple of [my] eye” (v. 8 KJV). The apple may be interpreted as the “pupil” of the eye. It is the gate, the very center of the eyeball, through which all light must pass. The eyeball is fiercely protected by the eyelid, which instinctively closes the moment anything threatening comes near the eye. In effect, the Lord is saying, “I am not only watching over you, but you are in my eye!”
If you walk closely to the Lord, you will never stray outside His “wall of fire,” and you will always be protected as the “pupil of His eye.” Fear not, citizen of Zion. Your God has awesome keeping power!