What did Christ's resurrection open the door to?
It opened the door to the whole doctrine of life after death, a doctrine that had to begin with the Creator Himself. Resurrection never occurred before Jesus was raised, and His rising demonstrated its power and fulfilled first fruits. This is a basic doctrine to rest on.
Les explains that resurrection, as precipitated by Christ's own resurrection, opened the door to the whole doctrine of life after death, beginning with the Creator Himself. He distinguishes this from earlier cases like Elijah’s and the widow’s son or Lazarus, which were merely bringing someone back to life only to die again. Resurrection never took place until Jesus was raised from the dead. Immediately after, to show its power and fulfill first fruits as practiced in the Old Testament economy, some were brought out of the graves around Jerusalem, entered the Holy City, and appeared to many.