"We didn't start the fire!" Responsibility (Achrayut) in the Jewish tradition

(16) Do not deal basely with your countrymen. Do not stand by the blood of your fellow: I am the LORD.

And furthermore, it is taught in a baraita: One may not sell weapons to gentiles or the auxiliary equipment of weapons, and one may not sharpen weapons for them. And one may not sell them stocks used for fastening the feet of prisoners, or iron neck chains [kolarin], or foot chains, or iron chains. This prohibition applies equally to both a gentile and a Samaritan. Abaye analyzes this baraita: What is the reason for the prohibition against selling these items to Samaritans? If we say that they are suspected of bloodshed, that is difficult: But are they suspected of this? Didn’t you say that one may seclude oneself with them, which indicates that they are not suspected of bloodshed? Rather, it is prohibited to sell these items to Samaritans because they will come to sell them to a gentile. According to this reasoning, it should likewise be prohibited to sell a donkey to a Jew who is suspected of selling animals to gentiles. And if you would say that there is a difference between a Jew and a Samaritan, as a Samaritan will likely not repent and will sell to a gentile, whereas a Jew will likely repent and not sell these items, this reasoning is incorrect. But doesn’t Rav Naḥman say explicitly that Rabba bar Avuh says: Just as the Sages said that it is prohibited to sell to a gentile, so too it is prohibited to sell to a Jew who is suspected of selling to a gentile? When Rabba heard this and realized that Abaye was correct, he ran three parasangs after the buyer who purchased his donkey to revoke the sale, as the Jew was suspected of selling to gentiles; and some say that he ran one parasang through sand. But he did not succeed in overtaking him. Apropos the baraita that discusses the prohibition against selling weapons, the Gemara relates that Rav Dimi bar Abba says: Just as it is prohibited to sell to a gentile, it is prohibited to sell to an armed bandit who is a Jew. The Gemara clarifies: What are the circumstances of this prohibition? If the thief is suspected of killing, isn’t it obvious that it is prohibited? After all, he is the same as a gentile. Providing a Jew who might kill with weapons is no different from giving a weapon to a gentile, as in both cases one violates the prohibition: Do not place a stumbling block before the blind. And if he is a bandit who does not kill, why not sell to him? The Gemara answers: Actually, Rav Dimi bar Abba is referring to a bandit who does not kill, and here we are dealing with a bandit who steals, as sometimes he makes use of his weapon to save himself when he is caught. Consequently, it is prohibited to sell him weapons in case he kills with them in self-defense.