What It is to Have Christ for a Foundation, and Who They are to Whom Salvation as by Fire is Promised
But if it be said that in the interval of time between the death of this body and that last day of judgment and retribution which shall follow the resurrection, the bodies of the dead shall be exposed to a fire of such a nature that it shall not affect those who have not in this life indulged in such pleasures and pursuits as shall be consumed like wood, hay, stubble, but shall affect those others who have carried with them structures of that kind; if it be said that such worldliness, being venial, shall be consumed in the fire of tribulation either here only, or here and hereafter both, or here that it may not be hereafter—this I do not contradict, because possibly it is true.
For perhaps even the death of the body is itself a part of this tribulation, for it results from the first transgression, so that the time which follows death takes its color in each case from the nature of the man's building. The persecutions, too, which have crowned the martyrs, and which Christians of all kinds suffer, try both buildings like a fire, consuming some, along with the builders themselves, if Christ is not found in them as their foundation, while others they consume without the builders, because Christ is found in them, and they are saved, though with loss; and other buildings still they do not consume, because such materials as abide for ever are found in them.
In the end of the world there shall be in the time of Antichrist tribulation such as has never before been. How many edifices there shall then be, of gold or of hay, built on the best foundation, Christ Jesus, which that fire shall prove, bringing joy to some, loss to others, but without destroying either sort, because of this stable foundation! But whosoever prefers, I do not say his wife, with whom he lives for carnal pleasure, but any of those relatives who afford no delight of such a kind, and whom it is right to love—whosoever prefers these to Christ, and loves them after a human and carnal fashion, has not Christ as a foundation, and will therefore not be saved by fire, nor indeed at all; for he shall not possibly dwell with the Saviour, who says very explicitly concerning this very matter, “He that loves father or mother more than me is not worthy of me; and he that loves son or daughter more than me is not worthy of me.” But he who loves his relations carnally, and yet so that he does not prefer them to Christ, but would rather want them than Christ if he were put to the proof, shall be saved by fire, because it is necessary that by the loss of these relations he suffer pain in proportion to his love. And he who loves father, mother, sons, daughters, according to Christ, so that he aids them in obtaining His kingdom and cleaving to Him, or loves them because they are members of Christ, God forbid that this love should be consumed as wood, hay, stubble, and not rather be reckoned a structure of gold, silver, precious stones. For how can a man love those more than Christ whom he loves only for Christ's sake?
Source: City of God (New Advent)