XV. But we add further that our church was in the papacy itself, in as much as God always preserved in the midst of Babylon a remnant for himself according to the election of Grace (to wit, true believers who, groaning under that captivity, panted for spiritual deliverance; who are said to have been in the papacy not as to communion with it [Since they disapproved of and turned away from its errors and superstitions], but as to tarrying and as guests because they lived in the midst of the papal church, not conjointly, but scattered through kingdoms, provinces, cities and families, in which God wonderfully preserved his people).
XVI. This is proved by many arguments. (1) from various passages of Scripture, as 2 Thessalonians 2:4, where it is said “the son of perdition and the man of sin will sit in the temple of God” (i.e., will exercise dominion in the church, everywhere designated by this name, which therefore would be oppressed and captive there). Also from Rev. 7:3, where the angels are prohibited from hurting the earth until “the servants of God are sealed in their foreheads,” to intimate that his pious worshipers, who constantly adhere to him in time of apostasy, are marked with the seal of God, so that the certain protection of them by God’s providence may be denoted. By this seal, they will be taken away from impending calamities, in allusion to the custom of kings who mark with their own seal what they do not wish to be touched (Dan 6:17); or to the custom of shepherds, who put a mark on their sheep that they may be known from others; or to the typical markings of the Old Testament by which exemption was procured from some destruction, separation from the others who were involved in it, as of the Israelites from the Egyptians (Ex 12:13), Of Rahab from the perishing (Jos 2:18), of those sighing among the people of God from the rest who were to be devoted to destruction (Ezek 9:4). This is a manifest sign—that in the midst of the corruption of the world the elect always remain faithful, whom God ever preserves under his mark and protection. Here belongs what is said in Rev 11:1, two concerning the measure of the temple and the altar and those that worshiped therein, while the court which is without is excluded and the city, which is to be trod underfoot by the Gentiles, to denote that God always saves the sanctuary and the church and true believers, who worship him with a pure heart, in the midst of the city (i.e., in the visible church, which is profaned and polluted by the uncircumcised Gentiles, that is, the impious and unbelieving). What is added (v. 3) concerning the “two witnesses prophesying” (i.e., The few asserters of divine truth), who should bewail with continual complaints the follow corruption of the church and would confirm the period of faith and of the gospel worship against the people errors and superstitions, both by words and works and with their own blood; and what is still further said (12:6) concerning the woman who is nourished in the wilderness, of the angels (i.e., the gospel preachers, 14:6, 7) and those commanded to come out of Babylon eight (18:4), this could not be said unless the people of God (i.e., the true church) was still to be in the midst of Babylon.
Francis Turretin, Institutes of Elenctic Theology, 18.10.15–16.