Back to the old Adventus Domini. I've made a kind of table of epistles but I had to put the sources all in quotes because who can say just what these sources actually are? For the Ambrosian and Mozarabic, I used this rendition. For the Medieval, I just backed in the old forgotten Sundays after Pentecost and, for Wuerzburg, I put in the epistle of Ember Saturday, as that Sunday was vacat. Then I colour-coded both near hits and misses.
Now we beseech you, brethren, by the coming of our Lord [adventum Domini] Jesus Christ, and by our gathering together unto him, that ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ [dies Domini] is at hand. Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. Remember ye not, that, when I was yet with you, I told you these things? And now ye know what withholdeth that he might be revealed in his time. For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way. And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming [adventus]: even him, whose coming [adventus] is after the working of Satan with all power and signs and lying wonders, and with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. And for this cause God shall send them strong delusion, that they should believe a lie: that they all might be damned who believed not the truth, but had pleasure in unrighteousness. But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth: whereunto he called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ.
This seminal passage, which features prominently in the other three, is totally missing from our tradition, where not a single lection from 2 Thessalonians survives. But what is being said here? Something critical. But I'll just let Wikipedia do the talking (my emphases in red):
The term is found in 2 Thessalonians 2:6-7 in an eschatological context: Christians must not behave as if the Day of the Lord would happen tomorrow, since the Son of Perdition (the Antichrist of 1 and 2 John) must be revealed before. Paul then adds that the revelation of the Antichrist is conditional upon the removal of "something/someone that restrains him" and prevents him being fully manifested. Verse 6 uses the neuter gender, τὸ κατέχον; and verse 7 the masculine, ὁ κατέχων.
The interpretation of this passage has raised many problems, since Paul does not speak clearly ...
In Nomos of the Earth, German political thinker Carl Schmitt suggests the historical importance within traditional Christianity of the idea of the katechontic "restrainer" that allows for a Rome-centered Christianity, and that "meant the historical power to restrain the appearance of the Antichrist and the end of the present eon." The katechon represents, for Schmitt, the intellectualization of the ancient Christianum Imperium, with all its police and military powers to enforce orthodox ethics (see Carl Schmitt, The Nomos of the Earth in the International Law of the Jus Publicum Europaeum, G.L. Ulmen, trs., (New York: Telos, 2003), pp. 59–60.) In his posthumously published diary the entry from December 19, 1947 reads: "I believe in the katechon: it is for me the only possible way to understand Christian history and to find it meaningful" (Glossarium, p. 63). And Schmitt adds: "One must be able to name the katechon for every epoch of the last 1,948 years. The place has never been empty, or else we would no longer exist."
That imperium is now falling away and with it the power of the "restrainer." Expect the arrival of the Man of Lawlessness. His footfall is almost upon the doorstep.