5 YHWH said to Moses, “Tell Aaron, ‘Stretch out your hand with your rod over the rivers, over the streams, and over the pools, and cause frogs to come up on the land of Egypt.’” Exodus 8:5WEB
This passage contains a positive command, with immediate application directed toward Aaron through Moses, "Stretch forth thy hand with thy rod over the rivers, over the streams, and over the pools, and cause frogs to come up upon the land of Egypt.".
This command is part of the Principles and Definitions. It is relevant to an understanding of the distinctive role of Prophecy as Moses is relaying a message from God, and as God said in Exodus 7:1-2, Aaron is acting as the prophet of Moses.
This command was fulfilled when Aaron acted in accordance with God's commands.