Albert Barnes Commentary Exodus 8:25

"And Pharaoh called for Moses and for Aaron, and said, Go ye, sacrifice to your God in the land." — Exodus 8:25 (ASV)

To your God - Pharaoh now admits the existence and power of the God whom he had professed not to know; but, as Moses is careful to record, he recognizes Him only as the national Deity of the Israelites.

In the land - that is, in Egypt, not beyond the frontier.