Continuing the theme of mipnei tikkun ha-olam – encouraging the proper workings of society – the Mishna on our daf teaches that a Jewish person who sells his field in Israel to a non-Jew is obligated to purchase fruit from the new owner and bring bikkurim – the offering of first fruits – to Jerusalem.
This version of the Mishna is Rashi’s, who understands that the tikkun olam involved is that the original owner is obligated to purchase fruit from the field – at any price – in order to fulfill the mitzva of bikkurim. This is done to encourage the original owner to rethink the sale and pressure him to buy the field back from the non-Jew.
According to most other rishonim – as well as the standard text in the Mishnayot and the Talmud Yerushalmi – the Mishna does not require the seller to purchase fruit from the field; rather, in a situation where another Jewish person purchases the field from the non-Jew, he will be obligated to bring bikkurim, even though the fruit grew in the possession of someone who was not obligated in this mitzva. Some rishonim suggest that this rule would also hold true in a case in which the field remained in the non-Jewish hands, but the fruit was purchased by a Jewish person; mipnei tikkun ha-olam, he would have to take bikkurim from the fruit that he bought.
The Ri”d suggests that this is because the mitzva of bikkurim takes place in the public eye with a colorful march to Jerusalem, and someone who doesn’t know that the land was sold will mistakenly think that the mitzva of bikkurim does not apply. With regard to the other tithes, which are all taken and arranged privately, the need for such a tikkun ha-olam was not as pressing. The Me’iri suggests that bikkurim is just an example and that someone who purchases the field or the fruit would be obligated in all of the agricultural tithes mipnei tikkun ha-olam.