I will let you go only ye shall not go very far away - Pharaoh relented because the hand of God was heavy upon him; but he was not willing to give up his gain. The Israelites were very profitable to him; they were slaves of the state, and their hard labor was very productive: hence he professed a willingness, first to tolerate their religion in the land, (Exodus 8:25); or to permit them to go into the wilderness, so that they went not far away, and would soon return. How ready is foolish man, when the hand of God presses him sore, to compound with his Maker! He will consent to give up some sins, provided God will permit him to keep others.

Entreat for me - Exactly similar to the case of Simon Magus, who, like Pharaoh, fearing the Divine judgments, begged an interest in the prayers of Peter, Acts 8:24.

I will

Hosea 10:2 Their heart is divided; now shall they be found faulty: he shall break down their altars, he shall spoil their images.

intreat

Exodus 8:8,29 Then Pharaoh called for Moses and Aaron, and said, Entreat the LORD, that he may take away the frogs from me, and from my people...

Exodus 9:28 Entreat the LORD (for it is enough) that there be no more mighty thunder and hail; and I will let you go, and you shall stay no longer.

Exodus 10:17 Now therefore forgive, I pray you, my sin only this once, and entreat the LORD your God, that he may take away from me this death only.

1 Kings 13:6 And the king answered and said to the man of God, Entreat now the face of the LORD your God, and pray for me...

Ezra 6:10 That they may offer sacrifices of sweet smells to the God of heaven, and pray for the life of the king, and of his sons.

Ecclesiastes 6:10 That which has been is named already, and it is known that it is man: neither may he contend with him that is mightier than he.

Acts 8:24 Then answered Simon, and said, Pray you to the LORD for me, that none of these things which you have spoken come on me.

Exodus
The book of Exodus--so named in the Greek version from the march of Israel out of Egypt--opens upon a scene of oppression very different from the prosperity and triumph in which Genesis had closed. Israel is being cruelly crushed by the new dynasty which has arisen in Egypt (i.) and the story of the book is the story of her redemption. Ultimately it is Israel's God that is her redeemer, but He operates largely by human means; and the first step is the preparation of a deliverer, Moses, whose parentage, …
John Edgar McFadyen—Introduction to the Old Testament