We are taught in Parashat Vayikra (VaYikra 5:23) that when someone steals something belonging to someone else, in addition to bringing a Korban Asham, a sin offering, “VeHeishiv Et HaGezeilah Asher Gazal,” “[the thief] must return what is stolen [to the owner].” This rule is simple enough in a normal case of theft, but complications can arise in special circumstances, for instance, a professional thief who does Teshuvah and consequently tries to return everything he had stolen. One day when leaving his home, he kisses his Mezuzah and remembers that the Mezuzah was actually stolen. After remembering this, he goes to the Judaica store from which he stole it and pays for it. The reformed thief now wonders whether he must take the Mezuzah down and put it back up again, because when he put it up, it was stolen, and he may not have fulfilled his Mitzvah of Mezuzah. This fascinating question is addressed by Rav Yitzchak Zilberstein in Teshuvot VeHa’arev Na.
Perhaps this case of the stolen Mezuzah can be compared to a case of stolen Tzitzit strings. The Bei’ur Halachah (Orach Chayim 11:6) discusses the case of someone who steals Tzitzit strings, attaches them to his four cornered garment, and only afterwards pays for them. Does the person need to retie them after paying for them? The principle which guides this question is the source for Tzitzit: “VeAsu LaHem Tzitzit,” “They shall make for themselves Tzitzit” (BeMidbar 15:38). Chazal (Menachot 33a) understand this to mean that the Tzitzit must be Kosher when they are made, i.e. when they are tied to the garment. This principle is known as “Ta’aseh VeLo Min HaAsuy,” that Tzitzit must be made [from rightfully owned materials], not from that which is already made. The question is: after the stolen Tzitzit are paid for, are they required to be reaffixed, or does the sin gets corrected as if they were never stolen, and the Tzitzit can be left alone? The Bei’ur Halachah does not answer the question; the Aruch HaShulchan (Orach Chayim 8:22), however, answers that the Tzitzit do not need to be re-tied, because the rule of “Ta’aseh, VeLo Min HaAsuy” applies only when the object involved is unfit. In this case, the Tzitzit themselves are fine, but there is a problem with the person himself, as he stole the Tzitzit. The Mitzvah is not valid only because the person himself is not valid, but if the person becomes valid (by paying for the Tzitzit), the Mitzvah also becomes valid, and the Tzitzit do not need to be retied. In contrast to the Aruch HaShulchan, the Kaf HaChaim (8:23) believes that the concept of “Ta’aseh, VeLo Min HaAsuy” does apply in such a case, and the Tzitzit would need to be retied.
Similarly, “Ta’aseh, VeLo Min HaAsuy” can also apply to a Mezuzah, i.e. the Mezuzah must be Kosher when attached, and if it is not Kosher when it is put up, it must be fixed. In this case of the stolen Mezuzah, then, the decision whether reaffixing the Mezuzah is necessary would depend on the debate between the Aruch HaShulchan and the Kaf HaChaim. Some Acharonim, however, say that the stolen Tzitzit and the stolen Mezuzah cannot be compared. Owning the Tzitzit is an important part of the Mitzvah, as the Pasuk says: “VeAsu LaHem Tzitzit,” “They shall make for themselves Tzitzit.” There is no parallel Pasuk in the Torah about needing to own a Mezuzah, and thus the stolen Mezuzah only falls under the category of “Miztvah HaBa’ah BeAveirah,” a Mitzvah that is accomplished through an Aveirah (in this case, the stealing of the Mezuzah), and the fact that one does not legally own it does not make the Mitzvah invalid.
It must be noted that “VeHeishiv Et HaGezeilah Asher Gazal” appears in conjunction with the requirement to offer a Korban Asham to attain total forgiveness, and in addition to the Korban, some sort of Vidui Devarim, or verbal confession, is certainly required (see Rambam Sefer HaMitzvot Asei 73). Therefore, the Pesukim would appear to support the conclusion that a full erasure of the sin does not occur with a mere Hashavat HaGezeilah alone, which would support the Kaf HaChaim’s ruling over the Aruch HaShulchan’s ruling; since the sin is not corrected with the returning of the object, the person is still considered invalid. In any case, reaffixing a Mezuzah is a matter of just a few seconds, and the best course of action in such a case would be Machmir and reaffix the Mezuzah.