Bava Kamma — Daf 66a

הם ולא ולדותיהם הוא דאתא ובית הלל תרתי שמעית מינה הם ולא שינויהם הם ולא ולדותיהם ובית הלל הכתיב גם גם לבית הלל קשיא

עד כאן לא פליגי אלא דמר סבר שינוי קונה ומ"ס אין שינוי קונה אבל לענין שלומי כ"ע כדמעיקרא משלם דקתני משלם תשלומי כפל ותשלומי ארבעה וחמשה כעין שגנב

לימא תיהוי תיובתא דרב דאמר רב קרן כעין שגנב משלם תשלומי כפל ותשלומי ד' וה' כשעת העמדה בדין אמר רבא טלאים כדמעיקרא דמים כשל עכשיו

אמר רבה שינוי קונה כתיבא ותנינא כתיבא (ויקרא ה, כג) והשיב את הגזלה אשר גזל מה ת"ל אשר גזל אם כעין שגזל יחזיר ואם לאו דמים בעלמא בעי שלומי

תנינא הגוזל עצים ועשאן כלים צמר ועשאן בגדים משלם כשעת הגזילה

א"נ לא הספיק ליתנו לו עד שצבעו פטור אלמא שינוי קונה

יאוש אמרי רבנן דניקני מיהו לא ידעינן אי דאורייתא אי דרבנן

אי דאורייתא מידי דהוה אמוצא אבידה מוצא אבידה לאו כיון דמייאש מרה מינה מקמי דתיתי לידיה קני ליה האי נמי כיון דמייאש מרה קני ליה אלמא קני

או דלמא לא דמיא לאבידה אבידה הוא דכי אתאי לידיה בהתירא אתיא לידיה אבל האי כיון דבאיסורא אתאי לידיה מדרבנן הוא

דאמור רבנן ניקני מפני תקנת השבים

ורב יוסף אמר יאוש אינו קונה ואפילו מדרבנן:

איתיביה רב יוסף לרבה גזל חמץ ועבר עליו הפסח

indicates 'them' and not their offsprings.  And Beth Hillel? — They reply that you can understand the two points from it: 'Them' — and not their transformations; 'them' — and not their offsprings. But as to Beth Hillel surely it is written Gam? — Gam presents a difficulty according to the view of Beth Hillel. Their  difference extends only so far that one Master  maintains that a change transfers and the other Master  maintains that a change does not transfer ownership, but regarding payment they both agree that the payment is made on the basis of the original value, even as it is stated:  'He has to make double payment or fourfold and five-fold payments on the basis of the value at the time of the theft.' Are we to say that this [Baraitha] confutes the view of Rab in the statement made by Rab that the principal will be reckoned as at the time of theft, whereas double payment or four-fold and five-fold payments will be reckoned on the basis of the value when the case comes into Court? — Said Raba: [Where he pays with] sheep, [he pays] in accordance with the original value,  but [where he pays with] money [he pays] in accordance with the present value. Rabbah said: That a change  transfers ownership is indicated in Scripture and learnt in Mishnah. It is indicated in Scripture in the words, He shall restore the misappropriated object which he violently took away.  What is the point of the words 'which he violently took away'? — It is to imply that if it is still as [it was when] he violently took it  he shall restore it, but if not, it is only the value of it that he will have to pay.  It is learnt [in the Mishnah]: If one misappropriates timber and makes utensils out of it, or wool and makes it into garments, he has to pay in accordance with the value at the time of robbery.  Or as also [learnt elsewhere]: If the owner did not manage to give the first of the fleece to the priest  until it had already been dyed, he is exempt,  thus proving that a change transfers ownership. So has Renunciation  been declared by the Rabbis to transfer ownership. We, however, do not know whether this rule is derived from the Scripture, or is purely Rabbinical. Is it Scriptural, it being on a par with the case of one who finds a lost article?  For is not the law in the case of a finder of lost property that, if the owner renounced his interest in the article before it came into the hands of the finder the ownership of it is transferred to the finder? So in this case, the thief similarly acquires title to the article as soon as the owner renounces his claim. It thus seems that the transfer is of Scriptural origin! Or are we to say that this case is not comparable to that of a lost article?  For it is only in the case of a lost article that the law applies, since when it comes into the hands of the finder,  it does so lawfully, whereas in the case of the thief into whose hands it entered unlawfully, the rule therefore might be merely of Rabbinic authority, as the Rabbis might have said that ownership should be transferred by Renunciation in order to make matters easier for repentant robbers. But R. Joseph said: Renunciation does not transfer ownership even by Rabbinic ordinance. R. Joseph objected to Rabbah's view [from the following:] If a man misappropriated leavened food [before Passover],  when Passover has passed