Shevuos, Chapter 7, Mishnah 2. This mishnah deals with the second of the cases of "nishba venotel" - one who may swear and collect on the strength of his oath.
"HaNigzal keitzad":
The mishnah asks how there could be a case in which a person from whom an object was stolen swears and collects. And this is the case: "Hayu me'idin oso shenichnas leveiso lemashkeno shelo bireshus" - there are witnesses who testify that the man we are claiming is a robber entered his fellow's house in order to take a security deposit without permission, for taking a security requires authorization from beis din. The witnesses saw him leaving the house with objects hidden under his coat, but they do not know what those objects were.
From here the claims divide:
"Kelai natalti" - the owner of the house from which the items were taken claims: those objects are mine, and you had no right to take them.
"Lo natalti" - the one who entered responds and denies, and his claim can be understood in two ways: that he took nothing at all and the witnesses are mistaken, since there is nothing under his clothing; or that the objects that were with him are his own.
The ruling: "Harei zeh nishba venotel" - the homeowner whose house was entered unlawfully swears and collects on the strength of his claim. The reason is a penalty that the Sages imposed on those who enter other people's houses and take their belongings, and therefore they permitted the victim to swear and collect.
The view of Rabbi Yehudah:
Rabbi Yehudah disagrees, consistent with his view in the previous mishnah, and holds that one swears only when the defendant admits to part of the claim. How so? The victim says: "You took two vessels," and the other responds: "I took only one" - that is, he admits that he indeed took one vessel, and denies the second.
In such a case there is a partial admission, but since the defendant is a robber, he is not permitted to swear; rather the victim, from whom the objects were taken, is the one who swears and collects on the strength of his oath.
In summary: In this mishnah we learned the second case of "nishba venotel" - the victim of robbery, concerning whom witnesses testify that the defendant entered his house to take a security without permission and left with vessels hidden under his coat. Because of the penalty imposed on robbers, the victim swears and collects according to his claim. Rabbi Yehudah requires a partial admission on the part of the defendant, and even in that case the oath falls upon the victim and not upon the robber.