10 Nor is there, alas, any just and weighty reason which excuses such a crime. One's country was to be left, and loss of one's estate was to be suffered. Yet to whom that is born and dies is there not a necessity at some time to leave his country, and to suffer the loss of his estate? But let not Christ be forsaken, so that the loss of salvation and of an eternal home should be feared. Behold, the Holy Spirit cries by the prophet, “Depart, depart, get out of there, touch not the unclean thing; get out of her midst, and be separate,you who bear the vessels of the Lord.” Yet those who are the vessels of the Lord and the temple of God do not go out from the midst, nor depart, that they may not be compelled to touch the unclean thing, and to be polluted and corrupted with deadly food.
Elsewhere also a voice is heard from heaven, forewarning what is becoming for the servants of God to do, saying, “Come out of her, my people, that you be not partakers of her sins, and that you receive not of her plagues.” He who goes out and departs does not become a partaker of the guilt; but he will be wounded with the plagues who is found a companion in the crime. And therefore the Lord commanded us in the persecution to depart and to flee; and both taught that this should be done, and Himself did it. For as the crown is given of the condescension of God, and cannot be received unless the hour comes for accepting it, whosoever abiding in Christ departs for a while does not deny his faith, but waits for the time; but he who has fallen, after refusing to depart, remained to deny it.
Source: The Treatises of Cyprian (New Advent)