Exodus 7:19-20

And the LORD spake unto Moses, Say unto Aaron, Take thy rod, and stretch out thine hand upon the waters of Egypt, upon their streams, upon their rivers, and upon their ponds, and upon all their pools of water, that they may become blood; and {that} there may be blood throughout all the land of Egypt, both in {vessels of} wood, and in {vessels of} stone. {pools...: Heb. gathering of their waters} And Moses and Aaron did so, as the LORD commanded; and he lifted up the rod, and smote the waters that {were} in the river, in the sight of Pharaoh, and in the sight of his servants; and all the waters that {were} in the river were turned to blood.