Israel is the apple of God’s eye. That is not a reference to a Cox’s Orange Pippin, but to the gry iris of the eye, which looks like an apple on end with the stalk in the middle and is the most sensitive part of the body. When anything – even a tiny speck of dust – touches that part of the eye, the eyelid clamps down to protect it. The word for ‘eyelid’ in Hebrew is usually translated in our Bibles as ‘keeper’. “The Lord is your keeper” for example, means “the Lord is your eyelid”. Anyone who touches the Lord’s people touches the most senitive part of Him and He will protect His people.
David Pawson (Ed Greg Haslam)
From the book "Preach the Word!: The Call and Challenge of Preaching Today"