Before Adam’s fall it was not necessary for him to have Christ, because he was righteous and without sin, just as the angels have no need of Christ. If Adam had not fallen, it would not have been necessary for Christ to become our Redeemer.
…The argument is true that eternal life is in the given to him who keeps the law without Christ, because whoever keeps the law is righteous. Adam would have entered into the kingdom of heaven without Christ, if he had not fallen.
…The conclusion is that Adam alone kept the commandments of God before the Fall, but after the Fall and no one has truly been found who has fulfilled the law
—Martin Luther, Disputatio de iustificatione, (1536) in Luther’s Works, 26.185, 187
John Owen wrote (Communion with God):
…how is it that Christ did not sin in the loins of Adam?
Answer. Christ was never legally represented by Adam, so was not liable to the imputation of Adam’s sin. … Had Adam not sinned, Christ would not have been incarnate. He would not have needed to be a Mediator for sinners. Therefore the moral necessity that Christ should be incarnate took place only after the fall. …
It’s good to see that Luther had fairly well developed views on the substance of the
Covenant of Works, even stating that Adam would have inherited eternal life had
he not sinned in the garden, it’s a pity though that his views weren’t as well developed
on the Lords supper!