Theophylact of Ohrid — as excerpted in the Catena Aurea on John 1:6-8

“But it will be said, that we do not allow John or any of the saints to be or ever to have been light. The difference is this: If we call any of the saints light, we put light without the article. So if asked whether John is light, without the article, thou mayest allow without hesitation that he is: if with the article, thou allow it not. For he is not very, original, light, but is only called so, on account of his partaking of the light, which cometh from the true Light.”