2. Pharaoh's Heart Hardened - Verses 3-5
In several places Pharaoh is said to have hardened his own heart. Apart from God's grace men will naturally rebel and move further and further from God. Whenever God ceases to restrain men their inherit depravity will cause them to wax worse and worse (Romans 1:24, 26, 28).
Here God is said to have hardened Pharaoh’s heart (verse 3). This is the just and judicial judgment of God upon man's sin. While we rejoice that God is perfectly holy, yet we realize that in hardening men He goes beyond the mere removal of restraints. He is never the author of sin yet He so orders things that the wicked are judged and His purposes are carried out (Deuteronomy 2:30, Joshua 11:19-20). God hardens men not by infusing evil into their nature but by:
a. False Prophets - II Thessalonians 2:11-12, Matthew 24:24.
Can we doubt that Pharaoh's magicians were an instrument in His hardening?
b. Satan - Luke 22:3-6.
Unsaved men are already under Satan's delusion (II Corinthians 4:4, Ephesians 2:2). God can justly allow Satan even greater power over those He would harden in a special way.
c. Circumstances - Matthew 6:13
How easily God can permit events that turn men's evil desires into actions. Let us all be humble. Sometimes it is only lack of opportunity that keeps men from open debauchery.
d. Man's mental state
Some of the Hebrew words used to refer to God's work of hardening men seem to refer to the firming up of one's resolutions. Perhaps we could say that while God does not instill evil convictions in men, yet He gives some men the courage of their convictions. Think of Pharaoh's persistent rebellion as Egypt is destroyed around him.

3. Meeting Pharaoh - Verses 6-9
Moses and Aaron were informed in advance of what they would face. The Lord may not give us the same knowledge in specific matters, but those who study the scriptures learn what to expect from men and God.
God often still sends us to proclaim His word to those who will not listen.

4. The First Sign - Verses 10-13
Remember that the signs done for Israel were done separately from those performed before Pharaoh (Exodus 4:29-31). Here is the first sign done before Pharaoh. Indeed this was to be a contest between God and the gods of Egypt.
It is important to note that one of Satan's favorite tools is the "supernatural" (II Thessalonians 2:9, Matthew 24:24). God's men are often withstood by Satan's workers (II Timothy 3:8). Satan's signs are accompanied by a denial or corruption of God's Word and are often permitted as a test of men's hearts (Deuteronomy 13:1-3, I Corinthians 11:19).
There has been much discussion as to how the magicians performed their works. Were they clever tricks or works of Satanic power? The Bible does not answer this question. It is not necessary that we understand all of Satan's ways, but to obey God. We do notice that the Lord's signs are in every way superior to Satan's "lying signs and wonders" (II Thessalonians 2:9). Think of the works of Christ and His apostles as contrasted with modern self-proclaimed "healers." Even the Egyptian magicians eventually confessed that Moses alone worked by the power of God (Exodus 8:19).

5. The First Plague - Verses 14-25
Now the contest becomes more severe. The Nile was the basis of life and religion in Egypt. They worshipped the river and its inhabitants. The waters fertilized and watered their crops, supplied them with fish, and remained the favorite beverage. In one stroke the water of this great river becomes blood. What a wake-up call to Egypt.
Notice the folly of Pharaoh's magicians. The last thing Egypt needed was more blood. Satan has power but it can never stay God's judgment (Daniel 4:35). Neither is it ever used for anyone’s benefit.
Consider also the mercy of God. This judgment lasted only seven days. The Egyptians were also allowed to dig for water and preserve their lives. The Lord is longsuffering. His blows become harder only as man continues to rebel. Remember that Moses had warned Pharaoh twice before this judgment fell.