Revelation 13:18

Then that abominable one will send his commands throughout every government by the hand at once of demons and of visible men, who shall say, "A mighty king has arisen upon the earth; come ye all to worship him; come ye all to see the strength of his kingdom: for, behold, he will give you corn; and he will bestow upon you wine, and great riches, and lofty honours. For the whole earth and sea obeys his command. Come ye all to him." And by reason of the scarcity of food, all will go to him and worship him; and he will put his mark on their right hand and on their forehead, that no one may put the sign of the honourable cross upon his forehead with his right hand; but his hand is bound. And from that time he shall not have power to seal any one of his members, but he shall be attached to the deceiver, and shall serve him; and in him there is no repentance. But such an one is lost at once to God and to men, and the deceiver will give them scanty food by reason of his abominable seal. And his seal upon the forehead and upon the right hand is the number, "Six hundred threescore and six." And I have an opinion as to this number, though I do not know the matter for certain; for many names have been found in this number when it is expressed in writing. Still we say that perhaps the scription of this same seal will give us the word I deny. For even in recent days, by means of his ministers-that is to say, the idolaters-that bitter adversary took up the word deny, when the lawless pressed upon the witnesses of Christ, with the adjuration, "Deny thy God, the crucified One." Of such kind, in the time of that hater of all good, will be the seal, the tenor of which will be this: I deny the Maker of heaven and earth, I deny the baptism, I deny my (former) service, and attach myself to thee, and I believe in thee. […]

"His number is the name of a man, and his number is Six hundred threescore and six." As they have it reckoned from the Greek characters, they thus find it among many to be teitan, for teitanhas this number, which the Gentiles call Sol and Phoebus; and it is reckoned in Greek thus: t three hundred, e five, i ten, t three hundred, a one, n fifty,-which taken together become six hundred and sixty-six. For as far as belongs to the Greek letters, they fill up this number and name; which name if you wish to turn into Latin, it is understood by the antiphrase Diclux, which letters are reckoned in this manner: since D figures five hundred, I one, C a hundred, L fifty, V five, X ten,-which by the reckoning up of the letters makes similarly six hundred and sixty-six, that is, what in Greek gives teitan, to wit, what in Latin is called Diclux; by which name, expressed by anti-phrases, we understand Antichrist, who, although he be cut off from the supernal light, and deprived thereof, yet transforms himself into an angel of light, daring to call himself light. Moreover, we find in a certain Greek codex antemoj, which letters being reckoned up, you will find to give the number as above: a one, n fifty, t three hundred, e five, m forty, o seventy, j two hundred,-which together makes six hundred and sixty-six, according to the Greeks. Moreover, there is another name in Gothic of him, which will be evident of itself, that is, genshrikoj, which in the same way you will reckon in Greek letters: g three, e five, n fifty, j two hundred, h eight, r a hundred, i ten, k twenty, o seventy, j also two hundred, which, as has been said above, make six hundred and sixty-six.

Such, then, being the state of the case, and this number being found in all the most approved and ancient copies [of the Apocalypse], and those men who saw John face to face bearing their testimony [to it]; while reason also leads us to conclude that the number of the name of the beast, [if reckoned] according to the Greek mode of calculation by the [value of] the letters contained in it, will amount to six hundred and sixty and six; that is, the number of tens shall be equal to that of the hundreds, and the number of hundreds equal to that of the units (for that number which [expresses] the digit six being adhered to throughout, indicates the recapitulations of that apostasy, taken in its full extent, which occurred at the beginning, during the intermediate periods, and which shall take place at the end) — I do not know how it is that some have erred following the ordinary mode of speech, and have vitiated the middle number in the name, deducting the amount of fifty from it, so that instead of six decads they will have it that there is but one. [I am inclined to think that this occurred through the fault of the copyists, as is wont to happen, since numbers also are expressed by letters; so that the Greek letter which expresses the number sixty was easily expanded into the letter Iota of the Greeks.] Others then received this reading without examination; some in their simplicity, and upon their own responsibility, making use of this number expressing one decad; while some, in their inexperience, have ventured to seek out a name which should contain the erroneous and spurious number. Now, as regards those who have done this in simplicity, and without evil intent, we are at liberty to assume that pardon will be granted them by God. […]

Here it says is wisdom: let him calculate the number of the beast and through the calculation let him find it. For I will not say, it says, a foreign and unusual calculation, nor one named with concealment and doubling, but a calculation well-worn and …

This calls for wisdom. Whoever has understanding, let him reckon the number of the beast, for the number of the beast, it says, is that of a man. Let us reckon the number that is to be received, so that in the number we might …