Chagigah 26 - Thieves who repented
We learned before that the ignorant people were not trusted about ritual purity. This lead to a problem: since clay vessels are often used for sacrifices, and since after use they becomes "leftovers" (or "notar") and hence must be broken, and furthermore, since no kilns were permitted in the Jerusalem - people could not obtain clay vessels that would ritually pure. Therefore, the Sages lifted their distrust of the ignorant, but only under specific circumstances: clay vessels manufactured between Jerusalem and Modiim, were declared ritually pure. This was only true for craftsmen in Modiim who were heading toward Jerusalem, and not for re-sellers.
If thieves entered a house and stole earthenware vessels, but then returned them - they are believed to say "we did not touch the inside," which would preserve the vessels for use with sacrifices. This sounds strange. Thieves are usually ignorant of the details of ritual purity, and if they entered a house, we should presume that every room in which they had the time to reach should have its vessels impure! - These are special thieves: they repented. Thus, they are believed about purity of sacrifices also.
Art: The fruit thief by Jean Raoux