The intent of the third sign.
Blood poured on the ground could symbolise nothing but war and destruction. That water should be turned into it implied that peace should be changed into war, prosperity into ruin, quiet and tranquillity into a horrible carnage. The special reference would be to the destruction of Pharaoh's host in the Red Sea; but the other ruinous plagues, as especially the fifth, the seventh, and the tenth, would be glanced at also. That the water became blood on touching the ground of Egypt would indicate that it was the land and people of Egypt who were to be the sufferers. A very dreadful vengeance was thus foreshadowed by the third sign, which should have warned the Pharaoh of the terrible results that would follow his resistance to God's will as proclaimed by Moses. To the Israelites, on the contrary, the sign was one assuring them of final triumph; that the blood of their enemies would be poured out like water in the coming struggle, and their resistance to God's will be signally punished.