Charles H. Spurgeon on Psalms 18:28

"For thou wilt light my candle," etc. The psalmist speaks in this place of artificial light; "a candle," or "lamp;" which has been supposed to be illustrated by the custom prevailing in Egypt of never suffering their houses to be without lights, but burning lamps even throughout the night, so that the poorest people would rather retrench part of their food than neglect it. Supposing this to have been the ancient custom, not only in Egypt, but in the neighbouring countries of Arabia and Judaea, "the lighting of the lamp" in this passage may have had a special allusion. In the parallel passage, 2 Samuel 22:29, Jehovah is figuratively styled the "lamp" of the psalmist, as above. —Richard Mant.

Verse 28 (first clause). "Thou also shalt" —when none else can. And notice, too, how here, and often elsewhere, the psalmist begins with speaking of God, and ends with speaking to him. So the bride in the Canticles, "Let him kiss me with the kisses of his mouth, for thy love is better than wine." —Dionysius the Carthusian (1471), quoted by J. M. Neale.