Tertullian, A Treatise on the Soul 55

We do not imagine the underworld as a mere hollow cavity or some cosmic sewer; we locate it in the pit of the earth, in a second vastness, a hidden depth buried in the planet's very bowels. Scripture says Christ spent three days of death in the heart of the earth (Matt 12:40) — that is, in its innermost, internal recess, covered over with earth, shut inside it, with the lower abysses still roofed above him. Since Christ, God because he is also man, died according to the Scriptures and was buried according to them (1 Cor 15:3-4), he here too satisfied the law by undergoing the form of human death among the dead; he did not ascend into the higher heavens before he descended into the lower parts of the earth (Eph 4:9), so that there he might make the Patriarchs and Prophets partakers of himself. You must therefore believe in a subterranean underworld region, and shove aside those who haughtily decide that the souls of the faithful are unworthy of the underworld — servants above their Lord, disciples above their Master — despising, if they can, the comfort of the resurrection waiting in Abraham's bosom (Luke 16:22).

They object, 'Christ went to the underworld in this very way so that we would not have to; but what difference remains between pagans and Christians if the dead share the same prison?' Very well: how exactly will a soul breathe its last into heaven while Christ is still seated at the Father's right hand (Ps 110:1; Heb 1:3), before God's command has been heard through the archangel's trumpet (1 Thess 4:16), before those whom the Lord's coming finds alive in the world have been caught up into the air together with the dead in Christ who rise first (1 Thess 4:17)? Heaven is open to no one while the earth still stands secure — or rather, sealed shut. The kingdoms of heaven will be unlocked only when the world's transaction is complete (Rev 6:12-14). Others may claim our rest lies in the ether with Plato's disciples, or in the air with Arius, or around the moon with the Stoics' Endymions; 'No,' you say, 'it is in paradise, to which the Patriarchs and Prophets, appendages of the Lord's resurrection, have already migrated from the underworld.'

But how did John, in the Spirit, see the region of paradise subject to the altar reveal no souls there except the martyrs' (Rev 6:9)? How did Perpetua, that bravest martyr, on the day of her passion, see only her fellow martyrs in her vision of paradise — unless paradise's doorkeeper admits no one except those who have died in Christ, not in Adam? A new death for God, an extraordinary death for Christ, receives a different, private hospitality. Recognize the difference between the pagan and the faithful in death. If you die for God, as the Paraclete urges (John 16:13), not in soft fevers and sickbeds but in martyrdoms; if you take up your cross and follow the Lord as he himself commanded (Matt 16:24); then all paradise is yours, and your blood is the key. You also have from us a booklet on Paradise in which we establish that every soul is held under guard among the dead until the Day of the Lord (1 Pet 3:19; Rev 20:13).