Reference for Bava Kamma 135:21
איתמר המוכר לפני יאוש רב נחמן אמר חייב רב ששת אמר פטור
Does not this show that Renunciation does not transfer ownership, in contradiction to the view of Rab? — Raba said: Do you really think that the text of this teaching is correct? For was it not taught in the concluding clause: 'If one stole [a sheep or an ox] and slaughtered it and another came and stole it, the first thief will make fourfold and five-fold payments [respectively], whereas the second has to pay nothing but the principal'? Now, is there any authority who maintains that a change in substance does not transfer ownership?<span class="x" onmousemove="('comment',' [Why not pay double to the first thief who had already become the legal owner through effecting a change in the substance of the article stolen?] ');"><sup>16</sup></span>