Exodus 8:18-19

18Then the Egyptian magicians tried to use their magic to make gnats appear. But they could not do it. The gnats were on all the people and on all the animals.

19Then the magicians said to Pharaoh, ‘This is the work of God.’ But there was no change in Pharaoh's thoughts. He would not listen to them. The Lord had said that this would happen, and it did!