I was informed about a mechanic whose prices are very cheap. I am concerned that his charges are low because he uses stolen parts to make the repairs.

Q: Do I have to refrain from hiring him to repair my car?

A: It is forbidden to purchase stolen merchandise from a thief. This transgression is very severe since it encourages the thief to steal, and one who does so violates the prohibition of placing a stumbling block before the blind — lifnei iveir (C.M. 356:1, 369:1). Although the thief could always travel to a place where they do not recognize him as a thief, the reasoning is that if he does not have local customers he will not continue to steal.

The maxim used by the Gemara (Kiddushin 56b) is that it is not the mouse that steals, it is the hole in which he hides the stolen food that is at fault (Rashi explains that were it not for the available hole to hide the stolen food, the mouse would not steal the food in the first place; Sma 369:1).

If one realizes that he has purchased stolen property, he is forbidden to benefit from it, even after the owner despaired of recovering it (C.M. 369:2). There are even authorities who maintain that one who purchases stolen property from the thief is himself a thief, since his purchase removes the stolen property permanently from the owner’s domain (shinuy reshus), and the owner’s only recourse is to be reimbursed rather than demand the return of his stolen property (Nesivos 34:5, cf. Ketzos).

It also does not matter if the thief is a gentile who stole from gentiles. The prohibition of theft is one of the Sheva Mitzvos Bnei Noach, and thus purchasing from a gentile thief also violates the prohibition of lifnei iveir (Shulchan Aruch Harav, Geneivah 23; see Imrei Yaakov 9, 23. Kesef Hakodashim 358 adopts a lenient position; see also Shitah Mikubetzes, B.K. 113a, d.h. “v’lo”).

It is also forbidden to purchase objects that are presumed stolen; therefore one may not purchase wool or milk from a shepherd unless it is evident that the shepherd is authorized to sell these items (C.M. 358:1). A shepherd who does not own any animals of his own may thus be suspected of stealing the owner’s wool or milk. However, it is permitted to purchase objects from thieves who, in addition to stolen property, have possessions that were legally acquired; one need not be concerned that one is purchasing stolen objects (Sema 358:2). Others contend that when most of a thief’s possessions were acquired by means of theft, one is prohibited from purchasing from him potentially stolen objects (Taz 369:3). If the thief physically altered the stolen object, even if the alteration could be reversed — which some authorities maintain does not constitute a kinyan for the thief — nevertheless, if one is not certain that the object was stolen, it is permitted to purchase it. Thus, for example, it is permitted to purchase a pillow filled with wool bought from a shepherd (ibid. 358:12).

Concerning your case, if you do not know that this repair part was stolen, and the mechanic has car parts that he acquired legally, you are permitted to purchase it, especially since it is unlikely that one would run a garage with only stolen parts. On the other hand, it is prohibited to purchase a bike from someone who sells used bikes at a significant discount when it is very likely the bike or its parts was stolen, even if it was stolen from gentiles.