ANSWER: The difficulty lies in the meaning of two words, "promise" and "perfect." Promise is here used for the thing promised, the resurrection of the body and the glorification of the soul and body in the likeness of the glorified God-man. This is the perfection for which the heroes of faith recorded in this chapter, "the Westminster Abbey of the Old Testament," are waiting till the Second Advent of Christ and the general resurrection. The souls of the blessed dead are neither unconscious, nor hidden away in some doleful place, but they are in heaven, according to the constant testimony of the New Testament Scriptures, enjoying all that is possible for disembodied spirits. They are in the heaven of glory, "with Christ, which is very far better" than perfect love to him on the earth, while they were subject to the limiting an instantaneous increase and perfection, "when soul and body will his glorious image bear." The history of the saints upon the earth must be finished before the completion of heaven comes on. So it may be very properly said that the patriarchs, prophets and ancient saints are waiting for the completion of our dispensation before their glory will be made perfect by the dawning of the day in which their bodies will live again. Blessed in their present condition, they are blessed also in their anticipation of a supreme and eternal perfection. Thus, the "promise" is the "perfection."
— Steele's Answers pp. 108-110.