Warning is here given to Pharaoh of the last and conquering plague which was now to be inflicted. This was the death of all the first-born in Egypt at once, which had been first threatened (Exod. 4:23; I will slay thy son, thy first-born ), but is last executed; less judgments were tried, which, if they had done the work would have prevented this. See how slow God is to wrath, and how willing to b...