22 And how great, too, are those things which in the meantime are happening in that respect on our behalf! Something is given for an example, that the anger of an avenging God may be known. But the day of judgment is still future which the Holy Scripture denounces, saying, “Howl, for the day of the Lord is at hand, and destruction from God shall come; for, lo, the day of the Lord comes, cruel with wrath and anger, to lay the earth desolate, and to destroy the sinners out of it.” And again: “Behold, the day of the Lord comes, burning as an oven; and all the aliens and all that do wickedly shall be as stubble, and the day that comes shall burn them up, says the Lord.” The Lord prophesies that the aliens shall be burnt up and consumed; that is, aliens from the divine race, and the profane, those who are not spiritually new-born, nor made children of God.
For that those only can escape who have been new-born and signed with the sign of Christ, God says in another place, when, sending forth His angels to the destruction of the world and the death of the human race, He threatens more terribly in the last time, saying, “Go and smite, and let not your eye spare. Have no pity upon old or young, and slay the virgins and the little ones and the women, that they may be utterly destroyed. But touch not any man upon whom is written the mark.” Moreover, what this mark is, and in what part of the body it is placed, God sets forth in another place, saying, “Go through the midst of Jerusalem, and set a mark upon the foreheads of the men that sigh and that cry for all the abominations that be done in the midst thereof.” And that the sign pertains to the passion and blood of Christ, and that whoever is found in this sign is kept safe and unharmed, is also proved by God's testimony, saying, “And the blood shall be to you for a token upon the houses in which you shall be; and I will see the blood, and will protect you, and the plague of diminution shall not be upon you when I smite the land of Egypt.” What previously preceded by a figure in the slain lamb is fulfilled in Christ, the truth which followed afterwards. As, then, when Egypt was smitten, the Jewish people could not escape except by the blood and the sign of the lamb; so also, when the world shall begin to be desolated and smitten, whoever is found in the blood and the sign of Christ alone shall escape.
Source: The Treatises of Cyprian (New Advent)