Charles Ellicott Commentary Exodus 8:10

"And he said, Against to-morrow. And he said, Be it according to thy word; that thou mayest know that there is none like unto Jehovah our God." — Exodus 8:10 (ASV)

That thou mayest know. —Compare Exodus 7:5; Exodus 7:17. Moses is not content that Pharaoh should simply acknowledge Jehovah as he had done (Exodus 8:8), but wishes him to be convinced that no other god can compare with Him.