Exodus 7

1 Just as Pharaoh rejected God, Pharaoh would also reject Moses. Even after much punishment followed by mercy, Pharaoh would continue to reject God. Nonetheless, Moses would wield God's authority against Pharaoh.
3 Pharaoh was both proud and stubborn. As history develops we see that Pharaoh first hardens his own heart against God's punishments. Eventually he relents, but he does so out of dread, and not out of repentance. When this happens, God supernaturally strengthens Pharaoh's resolve to accomplish two things. First God will perform more miracles to give indisputable proof to the world that He is the only God and He has great power.
4 Secondly, God would destroy Pharaoh's army so that they would not follow the Israelites into the land of Canaan to wage war against them.
7 This was the last section of Moses' life. The first 40 years were spent in Pharaoh's court. The second 40 years was spent in the wilderness. The third 40 years was spent leading the Israelites out of Egypt.
11 There are a few possible explanations for how the Egyptian sorcerers were able to mimic the miracles of God. The first possibility was that they used some kind of illusion or slight of hand to make it appear their rods had changed into serpents. They could have done an illusion where their rods remained rods but began to squirm like snakes. Most of us who have seen a good illusionist are amazed, even when we know that such things are mystical at all. An illusion like this might have been enough to convince Pharaoh. I suppose it is also possible that demonic forces played a role in any "real" or simulated transformations (Mat 24:24).
12 Even though God did not prevent the sorcerers from imitating the miracle, He shows that He is more powerful than they are by having Moses' rod swallow their rods.
13 Nonetheless, Pharaoh was unimpressed with the power of God. Many people remain unimpressed whether they see great or small miracles.
17 My understanding is that the Nile was itself worshiped as a god because it was a "source" of life, much as the sun is considered a source of life. For God to have power to turn this "river of life" into a river of blood would be a great display of His power. Certainly Pharaoh would notice.
19 This plague of blood would affect all the bodies of water in Egypt. Even all the stored water would become blood.
22 Using what water was found, Pharaoh's magicians made it appear that they could also turn water into blood. Two significant things to note about these imitation miracles is that first they were done in small quantities, and second the magicians could not turn the blood back into water.
23 Pharaoh may not have been as affected as the majority of people in Egypt. Even though he could not bath in the defiled Nile, his servants probably were able to satisfy his thirst with water they were able to find or with alternatives such as juices.
24 God mercifully allowed the Egyptians to find fresh water by digging around the riverbanks.
25 After a week God allowed the river to clear.