Exodus 9:1 -  4

"Then the Lord said to Moses, 'Go to Pharaoh and say to him, "This is what the Lord, the God of the Hebrews says: 'Let my people go, so that they may worship me.' If you refuse to let them go and continue to hold them back, the hand of the Lord will bring a terrible plague on your livestock in the field - on your horses, donkeys and camels and on your cattle, sheep and goats. But the Lord will make a distinction between the livestock of Israel and that of Egypt, so that no animal belonging to the Israelites will die."'" NIV translation

Pharaoh is warned again and reminded that the plague will not affect the people of God. The Egyptians used many types of animals in their pagan worship including a black bull named Apis and, once again, Pharaoh is being given the chance to surrender to the one true God.

Exodus 9:5 - 7

"The Lord set a time and said, 'Tomorrow the Lord will do this in the land.' And the next day the Lord did it: All the livestock of the Egyptians died, but not one animal belonging to the Israelites died. Pharaoh investigated and found that not even one of the animals of the Israelites had died. Yet his heart was unyielding and he would not let the people go." NIV translation

Even after seeing the fact that there was a difference between God's people and the Egyptians, Pharaoh still would not surrender. That reminds us that a Christian testimony is powerful but it is only the power of God that can change a heart.

Exodus 9:8 & 9

"Then the Lord said to Moses and Aaron, 'Take handfuls of soot from a furnace and have Moses toss it into the air in the presence of Pharaoh. It will become fine dust over the whole land of Egypt, and festering boils will break out on people and animals throughout the land.'" NIV translation

With Pharaoh's refusal, the next plague is executed without further warning. Up to this point, the judgments had to do with external possessions and, although they had a cost, nothing gets your attention like physical affliction.