And I am sure that the king of Egypt will not let you go, no, not by a mighty hand. The omniscient God knew that Pharaoh would not permanently submit to Him, not even after the ten plagues, but would deliberately harden himself against his better knowledge and thus invite destruction upon himself.
Related Commentaries of Exodus 3:19
Exodus 3:19
19 And I am sure that the king of Egypt will not leta you go, no, not by a mighty hand.