Dearly beloved congregation of our Lord Jesus Christ, last time we saw God reiterate His promise to reveal Himself through delivering His people from Pharaoh. This time, God dispatches Moses and Aaron into Pharaoh's presence to do a final pre-plague sign. It's one final warning, a final invitation to Pharaoh to turn before he actually feels the weight of Yahweh's heavy hand on him and his nation. So God gives to His prophets one final sign that will vindicate their claim to be messengers of a God superior to all the gods of Egypt. Of course, God knew that this sign would be duplicated and mocked, and He gave it anyway. We'll talk about that. But in terms of what the Holy Spirit is teaching us in this passage, we see that God's respectful and serious approach was rebuffed and disregarded by Pharaoh, whose heart was hard. It's a warning: Don't let your heart get hard. And it's a promise: God will, in general, bend over backwards to give you fair evidence that it's really Him and that you really ought to believe Him.