Exodus 9:10

6 And the next day the LORD did just that. All the livestock of the Egyptians died, but not one animal belonging to the Israelites died.

7 Pharaoh sent officials and found that none of the livestock of the Israelites had died. But Pharaoh’s heart was hardened, and he would not let the people go.

8 Then the LORD said to Moses and Aaron, “Take handfuls of soot from the furnace; in the sight of Pharaoh, Moses is to toss it into the air.

9 It will become fine dust over all the land of Egypt, and festering boils will break out on man and beast throughout the land.”

10 So they took soot from the furnace and stood before Pharaoh. Moses tossed it into the air, and festering boils broke out on man and beast.

11 The magicians could not stand before Moses, because the boils had broken out on them and on all the Egyptians.

12 But the LORD hardened Pharaoh’s heart, and he would not listen to them, just as the LORD had said to Moses.

13 Then the LORD said to Moses, “Get up early in the morning, stand before Pharaoh, and tell him that this is what the LORD, the God of the Hebrews, says: ‘Let My people go, so that they may worship Me.

14 Otherwise, I will send all My plagues against you and your officials and your people, so you may know that there is no one like Me in all the earth.

Read all of Exodus 9