Hellenica (2.3.15-2.3.19)

Then Critias (for he still treated Theramenes as a friend) replied that it was impossible for people who wanted to gain power not to put out of the way those who were best able to thwart them.

But when, on account of the great numbers continually—and unjustly—put to death, it was evident that many were banding together and wondering what the state was coming to, Theramenes spoke again, saying that unless they admitted an adequate number of citizens into partnership with them in the management of affairs, it would be impossible for the oligarchy to endure.

Accordingly Critias and the rest of the Thirty, who were by this time alarmed and feared above all that the citizens would flock to the support of Theramenes, enrolled a body of three thousand, who were to share, as they said, in the government.

Theramenes, however, objected to this move also, saying that, in the first place, it seemed to him absurd that, when they wanted to make the best of the citizens their associates, they should limit themselves to three thousand, as though this number must somehow be good men and true and there could neither be excellent men outside this body nor rascals within[*] it.