Exodus 9:4-7

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.’ ” 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.