Reference for Bava Metzia 29:12
א"ל התם הלואה הכא זביני
Now, to what [kind of transaction does this apply]? If [it applies] to a creditor [claiming the field for his debt], is he entitled to the produce of the field? Has not Samuel said: The creditor exacts payment from the improvement, [which means] from the improvement only, but not from the produce? It must therefore [be said that it applies] to one who bought [a field] from a robber!<span class="x" onmousemove="('comment',' [In which case the formula provides for compensation in respect of the improvement made by the buyer in the field.] How then could Samuel have said that the person who has bought a field from a robber and has to return it to the rightful owner cannot claim compensation for the improvement he made in it? ');"><sup>12</sup></span>