Why the resurrection?
St Ambrose says in ‘On the death of his brother Satyrus’ - “For the resurrection, as the very form of the word shows, is this, that what has fallen should rise again, that which died should come to life again. And this is the course and ground of justice, that since the action of body and soul is common to both (for what the soul conceived, the body carried out), each should come unto judgement, and each should be either given over to punishment or reserved for glory.”
Tertullian says in his ‘On the resurrection of the flesh’ - “Now, since the entire man consists of the union of the two natures, he must therefore appear in both, as it is right that he should be judged in his entirety. As therefore he lived, so also must he be judged, because he has to be judged concerning the way in which he lived.”