Ye shall not go very far away — Not so far but that he might fetch them back again. It is likely he suspected that if once they left Egypt, they would never come back; and therefore when he is forced to consent that they shall go, yet he is not willing they should go out of his reach. See how ready God is to accept sinners submissions. Pharaoh only says, Intreat for me — Moses promises immediately, I will intreat the Lord for thee; and that he might see what the design of the plague was, not to bring him to ruin, but to repentance.
Related Commentaries of Exodus 8:28
Exodus 8:28
28 And Pharaoh said, I will let you go, that ye may sacrifice to the LORD your God in the wilderness; only ye shall not go very far away: intreat for me.