Epistle of Barnabus:
The final stumbling-block (or source of danger) approaches, concerning which it is written, as Enoch says, “For this end the Lord has cut short the times and the days, that His Beloved may hasten; and He will come to the inheritance.” And the prophet also speaks thus: “Ten kingdoms shall reign upon the earth, and a little king shall rise up after them, who shall subdue under one three of the kings.” In like manner Daniel says concerning the same, “And I beheld the fourth beast, wicked and powerful, and more savage than all the beasts of the earth, and how from it sprang up ten horns, and out of them a little budding horn, and how it subdued under one three of the great horns.”
Let no one imagine that he performs these wonders by divine power, but by the working of magic. And we must not be surprised if, since the demons and apostate spirits are at his service, he through their means performs wonders, by which he leads the inhabitants of the earth astray. John says further: “And he shall order an image of the beast to be made, and he shall give breath to the image, so that the image shall speak; and he shall cause those to be slain who will not adore it.” He says also: “And he will cause a mark [to be put] in the forehead and in the right hand, that no one may be able to buy or sell, unless he who has the mark of the name of the beast or the number of his name; and the number is six hundred and sixty-six,” that is, six times a hundred, six times ten, and six units. [He gives this] as a summing up of the whole of that apostasy which has taken place during six thousand years.
And there is therefore in this beast, when he comes, a recapitulation made of all sorts of iniquity and of every deceit, in order that all apostate power, flowing into and being shut up in him, may be sent into the furnace of fire. Fittingly, therefore, shall his name possess the number six hundred and sixty-six, since he sums up in his own person all the commixture of wickedness which took place previous to the deluge, due to the apostasy of the angels. For Noah was six hundred years old when the deluge came upon the earth, sweeping away the rebellious world, for the sake of that most infamous generation which lived in the times of Noah. And [Antichrist] also sums up every error of devised idols since the flood, together with the slaying of the prophets and the cutting off of the just. For that image which was set up by Nebuchadnezzar had indeed a height of sixty cubits, while the breadth was six cubits; on account of which Ananias, Azarias, and Misael, when they did not worship it, were cast into a furnace of fire, pointing out prophetically, by what happened to them, the wrath against the righteous which shall arise towards the [time of the] end. For that image, taken as a whole, was a prefiguring of this man’s coming, decreeing that he should undoubtedly himself alone be worshipped by all men. Thus, then, the six hundred years of Noah, in whose time the deluge occurred because of the apostasy, and the number of the cubits of the image for which these just men were sent into the fiery furnace, do indicate the number of the name of that man in whom is concentrated the whole apostasy of six thousand years..-ibid
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. -ibid
For if there are many names found possessing this number, it will be asked which among them shall the coming man bear. It is not through a want of names containing the number of that name that I say this, but on account of the fear of God, and zeal for the truth: for the name Evanthas (Euanqas) contains the required number, but I make no allegation regarding it. Then also Lateinos (Lateinos) has the number six hundred and sixty-six…Teitan too, is rather worthy of credit. For it has in itself the predicted number…We will not, however, incur the risk of pronouncing positively as to the name of Antichrist; for if it were necessary that his name should be distinctly revealed in this present time, it would have been announced by him who beheld the apocalyptic vision. -ibid