Exodus 7:14-9:7

"'This is the finger of God!' the magicians exclaimed to Pharaoh. But Pharaoh’s heart remained hard. He wouldn’t listen to them, just as the LORD had predicted." v8:19
Some people think, If only I could see a miracle, I could believe in God." God gave Pharaoh just such an oportunity. When gnats infested Egypt, even the magicians agreed that this was God's work ("the finger of God") - But still Pharaoh refused to believe. He was stubborn, and stubbornness can blind a person to the truth. When you rid yourself of stubbornness, you may be surprised by abundant evidence of God's work in your life.

Taken from the NLT Life Application Study Bible