Now the Lord said to Moses, “One more plague I will bring on Pharaoh and on Egypt; after that he will let you go from here. When he lets you go, he will assuredly drive you out from here completely.
-- Exodus 11:1
According to this verse God is telling Moses that not only will they let you go and worship, they won’t want you back. It answers the question about why they left with no intention of returning. The leaving without returning was the point, but now it was the Egyptian’s idea. They had had enough, and this fight had been too expensive. At that point, while holding their dead first born’ they just wanted them gone. I know they changed their mind after a few days, but it was too late. Lots of us have a hard time making up our minds, even about God and his place in our lives, but he is unchanging, and he continues to want us when we are not so sure. He promises to never leave us or forsake us, and that is a promise.
But the Lord hardened Pharaoh’s heart, and he was not willing to let them go. 28 Then Pharaoh said to him, “Get away from me! Be careful, do not see my face again, for on the day you see my face, you shall die!” 29 Moses said, “You have spoken correctly; I shall never see your face again!”
-- Exodus 10:27-29
Neither one was right. Moses got to see him once more, to tell him that all the firstborn sons would die, but Pharaoh didn’t kill Moses. We say things in the heat of anger and live to regret it. Pharaoh held out to the bitter end and it cost him his son, and all the other firstborn sons throughout the nation. We come off bad when we fight against God, because it is a forgone conclusion who will win. Even when the devil seemed to win and Jesus went to the cross, it was the biggest victory ever, for Jesus and for us.
So Moses and Aaron went to Pharaoh and said to him, “This is what the Lord, the God of the Hebrews says: ‘How long will you refuse to humble yourself before Me? Let My people go, so that they may serve Me. 4 For if you refuse to let My people go, behold, tomorrow I will bring locusts into your territory.
-- Exodus 10:3-4
God is on his throne, and you are not God. Both are true statements and Pharaoh could not come to terms with either one of them. Being a god king and being humble did not compute, they just didn’t go together, which left Pharaoh in a difficult position. He could keep up appearances or give into God. He chose to keep up appearances, which brought his downfall. Most of us have no power and still we have trouble being humble, we want to keep up appearances and our relationship with God suffers. We all have a relationship with God because he made us and owes us, but for many of us it is broken. Humility will fix it.