"Moses returned to the Lord and said, 'Why, Lord, why have you brought trouble on this people? Is this why you sent me? Ever since I went to Pharaoh to speak in your name, he has brought trouble on this people, and you have not rescued your people at all.'" NIV translation
God had already given Moses the details of what He was going to do but, with the conflict between him and the Israelite leaders, he questioned God's timing. We all must admit that, even as Christians, we sometimes wonder about God's purpose and timing.