Charles Spurgeon Commentary Exodus 10:8-9

"And Moses and Aaron were brought again unto Pharaoh: and he said unto them, Go, serve Jehovah your God; but who are they that shall go? And Moses said, We will go with our young and with our old; with our sons and with our daughters, with our flocks and with our herds will we go; for we must hold a feast unto Jehovah." — Exodus 10:8-9 (ASV)

Pharaoh was inclined to make terms with Moses, but God will have no conditions with those who are rebelling against him. An unconditional surrender is all that God will accept.