I have said to you: Release my son, so that he may serve me. And you were not willing to release him. Behold, I will put to death your firstborn son.’
Other versions
King James Version
And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn.English Standard Version
and I say to you, "Let my son go that he may serve me." If you refuse to let him go, behold, I will kill your firstborn son.'"New International Version
and I told you, "Let my son go, so he may worship me." But you refused to let him go; so I will kill your firstborn son.'"