And I know that the king of Egypt will not give you leave to go, no, not by a mighty hand.

And I am certain that the king of Egypt will not let you go without being forced.

εγω δε εξευρω, οτι δεν θελει σας αφησει ο βασιλευς της Αιγυπτου να υπαγητε, ειμη δια χειρος κραταιας·

And I am sure that the king of Egypt will not let you go, no, not by a mighty hand.