Exodus 9:7, 12, 34-35

The king sent people to see what had happened to the animals of Israel, and they found that not one of them had died. But the king was still stubborn and did not let the people go.

But the LORD made the king stubborn, so he refused to listen to Moses and Aaron, just as the LORD had said.

When the king saw that the rain, hail, and thunder had stopped, he sinned again, and he and his officers became stubborn. So the king became stubborn and refused to let the Israelites go, just as the LORD had said through Moses.