7. But let no one tolerate any who say that one is the Creator of the light, and another of darkness: for let him remember how Isaiah says, I am the God who made the light, and created darkness. Why, O man, art thou vexed thereat? Why art thou offended at the time that is given thee for rest? A servant would have had no rest from his masters, had not the darkness necessarily brought a respite. And often after wearying ourselves in the day, how are we refreshed in the night, and he who was yesterday worn with toils, rises vigorous in the morning because of the night’s rest? And what more helpful to wisdom than the night? For herein oftentimes we set before our minds the things of God; and herein we read and contemplate the Divine Oracles. And when is our mind most attuned to Psalmody and Prayer? Is it not at night? And when have we often called our own sins to remembrance? Is not at night? Let us not then admit the evil thought, that another is the maker of darkness: for experience shews that this also is good and useful.
St. Cyril of Jerusalem, Catechetical Lectures, NPNF 2 .7, lecture 9, ON THE WORDS, MAKER OF HEAVEN AND EARTH, AND OF ALL THINGS VISIBLE AND INVISIBLE