John 9:5 - Ellicott's Commentary On The Whole Bible

As long as I am in the world, I am the light of the world. — Better, when I am in the world. The thought is that the two things necessarily co-exist. He is the true Light, and this true Light cannot be in the world without shining in its darkness. (Comp. Note on John 1:5.) The thought is here closely connected with His teaching in the Temple but a short time before (John 8:12, “I am the Light of the world”), and also with the removal of physical and spiritual darkness which immediately followed.