Avodah Zarah 26
Rava said: [Disabling is here avoided] because it seems like inflicting a blemish on sanctified things. “Seems!” This is a real blemish! This is true only while the Temple was in existence, so that the animal is fit for being offered up; but at the present time, since it cannot in any case be offered, the prohibition does not apply.
But let it be regarded as inflicting a blemish on a blemished animal which, even though not fit for a sacrificial purpose, is forbidden! An animal which had been blemished, while it cannot be used for sacrifice, the money obtained for it may be used; but this excludes our case where the animal is not fit for the money obtained for it nor for actual sacrifice.
Yonah found R. Ilai as he was standing at the gate of Tyre. He said to him: They taught, “Cattle [bought at the idolatrous fair] should be disabled.” What about a slave? I am not asking about a Jewish slave; what I am asking about is a Canaanite slave. What is the law? The other replied: Why do you ask at all? It has been taught; As to idolaters and [Jewish] shepherds of small cattle, even though one is not obligated to take them out [of a pit], one must not throw them in [to a pit to endanger their lives].
Yirmiyah said to R. Zera: It was taught, “We may buy cattle from them, slaves and maidservants.” Is this to be applied to a Jewish slave or to a Canaanite slave as well? He said back: It makes sense that it refers only to a Jewish slave; for were it to apply to a Canaanite slave, why would he want him? When Ravin came he said in the name of Resh Lakish: It may apply even to a Canaanite slave; because he brings him under the wings of the Shekhinah.
Ashi said: When it comes to buying animals [from idolaters] is this bringing them under the wings of the Shekhinah? Rather, it is allowed because this diminished [the possessions of the idolaters], and here too it is allowed because this diminishes their possessions.
Yaakov once bought sandals [at the idolatrous fair], while R. Yirmiyah bought bread. One said to the other: “Orphan! Would your master act thus?” The other said back: “Orphan! Would your master act thus?” Both in fact had bought of private individuals, but each one thought that the other had bought from a dealer; for R. Abba the son of R. Hiyya b. Abba said: The prohibition was taught only in the case of buying from a dealer from whom tax is exacted, but buying from a private person from whom no tax is exacted is permitted.
Abba son of R. Hiyya b. Abba said: Had R. Yohanan been present once in a place where taxes were exacted even from private persons he would have forbidden [even such purchase]. How is it then that they made the purchase? They bought from a private individual who was not a permanent resident.
The following things are forbidden to be sold to idolaters: iztroblin, bnoth-shuah with their stems, frankincense, and a white rooster. Rabbi Judah says: it is permitted to sell a white rooster to an idolater among other roosters; but if it be by itself, one should clip its spur and then sell it to him, because a defective [animal] is not sacrificed to an idol.