Exodus 8:16 & 17

"Then the Lord said to Moses, 'Tell Aaron, "Stretch out your staff and strike the dust of the ground," and throughout the land of Egypt the dust will become gnats.' They did this, and when Aaron stretched out his hand with the staff and struck the dust of the ground, gnats came on people and animals. All the dust throughout the land of Egypt became gnats." NIV translation

The pattern of warning is changed now as Moses and Aaron immediately executed the next plague. The gnats were probably lice or ticks and was a direct attack on their earth "god" Geb. This reminds us that there is a point where God will stop warning us of our need to repent and He will initiate judgment.

Exodus 8:18 & 19

"But when the magicians tried to produce gnats by their secret arts, they could not. Since the gnats were on people and animals everywhere, the magicians said to Pharaoh, 'This is the finger of God.' But Pharaoh's heart was hard and he would not listen, just as the Lord had said." NIV translation

When the magicians could not duplicate the plague, they informed Pharaoh that it was the hand of God. Even with the testimony of his prized magicians, Pharaoh still rejected the will of God.

This reminds us that our surrender to Jesus as Savior and Lord is not based on what someone else says but on what is at work in our hearts.