Exodus 8:9-10

And Moses said to Pharaoh, “I am entirely at your service: when shall I plead [with the Lord] for you and your servants and your people, so that the frogs may leave you and your houses and remain only in the Nile?” Then Pharaoh said, “Tomorrow.” Moses replied, “May it be as you say, so that you may know [without any doubt] and acknowledge that there is no one like the LORD our God.