"Then the Lord said to Moses, 'Go, tell Pharaoh king of Egypt to let the Israelites go out of his country.' But Moses said to the Lord, 'If the Israelites will not listen to me, why would Pharaoh listen to me, since I speak with faltering lips?'" NIV translation
Even though the Israelites did not believe God and Moses, God still told him to go to Pharaoh.
Moses' reply was to wonder why Pharaoh would listen when his own people would not. He was still looking at his strength instead of trusting in God.
That is what the devil tries to get us to do as Christians. When we focus on ourselves and our own abilities, we lose track of the fact that God has already taken care of our infirmities. With our eyes focused on His promised deliverance, we can walk in true freedom.