Nedarim 44

אמר תהא שדה זו מופקרת ליום אחד לשבת אחת לחדש אחד לשנה אחת לשבוע אחת עד שלא זכה בה בין הוא בין אחר יכול לחזור בו משזכה בה בין הוא בין אחר אין יכול לחזור בו רישא רבנן סיפא רבי יוסי

If one said: This field will be ownerless for one day, for one week, for one month, for one year, or for one seven-year Sabbatical cycle, as long as no one took possession of the field, neither the one who declared it ownerless nor another person, he is able to retract his declaration. Once one took possession of the field, whether it is he or whether it is another person, he is unable to retract his declaration. This baraita is difficult, as the first clause is apparently in accordance with the opinion of the Rabbis, who hold that rendering property ownerless is unilateral and not contingent upon whether one took possession of it, and the latter clause is in accordance with the opinion of Rabbi Yosei, who holds that rendering property ownerless is complete only when one takes possession of that property.

אמר עולא סיפא נמי רבנן היא אי הכי אמאי עד שלא זכה בה בין הוא בין אחר יכול לחזור בו שאני שנה ושבוע דלא שכיחי

Ulla said: The latter clause is also in accordance with the opinion of the Rabbis. The Gemara asks: If so, why is the ruling in the baraita: As long as one did not take possession of the field, neither the one who declared it ownerless nor another person, he is able to retract his declaration; according to the Rabbis, once he declared the property ownerless, although he can take possession of it, he is unable to retract the declaration. The Gemara answers: It is different when one declares an item ownerless for a year or a seven-year period, as doing so is uncommon. Since from the outset he limited the duration of ownerless status, clearly he reserved for himself certain rights; therefore, he can retract his declaration.

ריש לקיש אמר מדסיפא רבי יוסי רישא נמי רבי יוסי ורישא היינו טעמא דלא לישתכח תורת הפקר

Reish Lakish said: From the fact that the latter clause is in accordance with the opinion of Rabbi Yosei, the first clause is also in accordance with the opinion of Rabbi Yosei. And in the first clause, this is the reason that one cannot retract his declaration once three days have passed: It is an ordinance instituted by the Sages to ensure that the halakhic status of ownerlessness would not be forgotten. If one could retract his declaration of ownerless status after three days, people would not distinguish between a case where another took possession, where, according to Rabbi Yosei, one is unable to retract the declaration, and a case where another did not take possession, where, according to Rabbi Yosei, one is able to retract the declaration. The result would be that people would mistakenly conclude that ownerless status can always be reversed, even after it was claimed by another. Therefore, the Sages instituted a limit of three days, after which one may not retract his declaration.

אי הכי אפילו מיום הראשון נמי ליהוי הפקר אמר רבה מפני הרמאין דמפקירין והדרין בהון

The Gemara asks: If so, then let the Sages institute that the item is considered ownerless even from the first day as well and that he cannot retract his declaration at all. Rabba said: The reason that the Sages did not render the item ownerless from the first day is due to the swindlers, who declare the field ownerless in order to render the produce of the field exempt from the requirement of tithing, and then retract that declaration and immediately reclaim the field. Therefore, the Sages instituted that ownerless status takes effect only after three days.

אבל דאורייתא לא הוי הפקר

The Gemara asks: The Sages instituted that one cannot retract his declaration of ownerless status once three days have passed. However, by Torah law, isn’t the item ownerless according to Rabbi Yosei, regardless of when he retracted his declaration as long as no other person acquired it?

ודלמא אתי לעשורי מן החיוב על הפטור ומן הפטור על החיוב

And that ordinance could lead to a problem, as perhaps he will come to tithe from produce that requires tithing by Torah law for produce exempt from tithing by Torah law and from produce exempt from tithing by Torah law for produce that requires tithing by Torah law. By Torah law, the produce is not ownerless and requires tithing. However, due to the ordinance, people might relate to it as ownerless produce and assume that one is exempt from tithing it. Alternatively, they will erroneously conclude that the obligation to tithe from that produce is by rabbinic law and will tithe produce from it that one is exempt from tithing by Torah law, or they will tithe that produce from produce that one is exempt from tithing by Torah law. The result will be produce that is not properly tithed, as one may tithe produce that one is obligated to tithe by Torah law only from other produce that one is obligated to tithe by Torah law.

דאמרינן ליה כי מעשרת עשר מיניה וביה

The Gemara answers: That problem will not arise, because if the declaration of ownerless status is retracted after three days, we say to the person who ultimately takes possession of the produce: When you tithe, tithe from that produce itself. In that way, the above problem does not arise.

מיתיבי המפקיר את כרמו ולשחר עמד ובצרו חייב בפרט ובעוללות ובשכחה ובפיאה ופטור מן המעשר

The Gemara raises an objection from a baraita: One who declares his vineyard ownerless, and at dawn he arose and picked grapes from the vineyard, is obligated in the mitzva of leaving individual fallen grapes left for the poor [peret], and in the mitzva of leaving incompletely formed clusters of grapes for the poor [olelot], and in the mitzva of leaving forgotten sheaves, and in the mitzva of pe’a, produce from the corner of the field or vineyard, as the obligation to separate those gifts from the poor is incumbent upon the one who harvests the field (see Leviticus 19:9–10). And he is exempt from the obligation to separate the tithe from the grapes. Because the vineyard is ownerless, there is no obligation to tithe the produce.

בשלמא לעולא דרבנן קתני לה ודאורייתא קתני לה אלא לריש לקיש אמאי פטור מן המעשר

The Gemara asks: Granted, this is so according to Ulla, who explained that the Rabbis taught the previous baraita and explains that although the Sages instituted that the ownerless status does not take effect completely until three days have passed, by Torah law it takes effect immediately, and that this baraita is taught in accordance with Torah law. That is the reason that one is exempt from tithing the grapes. However, according to Reish Lakish, why is he exempt from separating the tithe? Until three days after the declaration, neither by Torah law nor by rabbinic law does ownerless status take effect.

אמר לך כי אמרי אנא לרבי יוסי הא רבנן היא

The Gemara answers that Reish Lakish could have said to you: Although when I explained the first clause and the latter clause of that baraita I said that both are in accordance with the opinion of Rabbi Yosei, who said that an ownerless item leaves the possession of the owner only when it enters the possession of another, this baraita is in accordance with the opinion of the Rabbis, who hold that it leaves the possession of the owner immediately upon the declaration of ownerless status.