Exodus 8:28

28So Pharaoh said, “I will let you go to sacrifice to the Lord your God in the wilderness; only you must not go very far away. aPlead for me.”

Exodus 9:28

28 bPlead with the Lord, for there has been enough of God’s thunder and hail. I will let you go, and you shall stay no longer.”

Exodus 10:8-9

8So Moses and Aaron were brought back to Pharaoh. And he said to them, cGo, serve the Lord your God. But which ones are to go?” 9Moses said, “We will go with our young and our old. We will go with our sons and daughters and with our flocks and herds, for dwe must hold a feast to the Lord.”
Copyright information for ESV