Exodus 9:4-7

But the LORD will again make a distinction between the livestock of the Israelites and that of the Egyptians. Not a single one of Israel’s animals will die! The LORD has already set the time for the plague to begin. He has declared that he will strike the land tomorrow.’” And the LORD did just as he had said. The next morning all the livestock of the Egyptians died, but the Israelites didn’t lose a single animal. Pharaoh sent his officials to investigate, and they discovered that the Israelites had not lost a single animal! But even so, Pharaoh’s heart remained stubborn, and he still refused to let the people go.