Explanation: Pharaoh refused for a couple of reasons. One was the perceived financial loss if all the free labor would cease, as he himself implied (Exodus 14:5). Another was sheer obstinacy, in which he hardened his heart.
A careful reading of Exodus (ch.7-12), at least in the original Hebrew, reveals that Pharaoh hardened his own heart in most of the plagues. God only hardened Pharaoh's heart in three of the ten plagues: the sixth, eighth and ninth. That's all.
Then after the last plague Pharaoh was angry and released the Israelite to go to the promised land
