Targum zu Schemot 8:2

And Aharon uplifted his hand over the waters of Mizraim, and the plague of frogs came up and covered the land of Mizraim. But Mosheh (himself) did not smite the waters, either with the blood or with the frogs because through them (the waters of the Nile) he had (found) safety the time that his mother laid him in the river.