Charles H. Spurgeon on Psalms 105:28

Darkness. There is an awful significance in this plague of darkness. The sun was a leading object of devotion among the Egyptians under the name of Osiris. The very name Pharaoh means not only the king but also the sun, and characterises the king himself as the representative of the sun and entitled in some sort to divine honours. But now the very light of the sun has disappeared and primeval chaos seems to have returned. Thus all the forms of Egyptian will worship were covered with shame and confusion by the plagues. James G. Murphy, in "A Commentary on Exodus," 1866.