v. 19 — Command with maximal scope
Aaron is to stretch out the staff over Egypt’s "waters" (): rivers, streams, pools, and gathered bodies. The stated goal is that they become "blood" (), extending even to water held in wood and stone containers.
v. 20 — Execution before royal witnesses
Moses and Aaron do as instructed in the sight of Pharaoh and his servants. The strike targets the river, and the narrative reports an immediate transformation of the river’s water.
v. 21 — Observable consequences
Fish die, the river becomes foul, and Egyptians cannot drink from it. The text reiterates total reach across , underscoring that the disruption is not localized.