Sukkah 39B

ובא ואוכלן בקדושת שביעית.

And then he comes home and eats the produce in the appropriate manner and at the appropriate time, due to the sanctity of Sabbatical-Year produce.

במה דברים אמורים ⁠— בלוקח מן המופקר. אבל בלוקח מן המשומר, אפילו בכחצי איסר ⁠— אסור.

The baraita continues: In what case is this statement said that it is permitted to transfer money used to purchase Sabbatical-Year produce to an am ha’aretz as long as it does not exceed the value of 3 meals? It is specifically in a case where one purchases produce that came from a field that was declared ownerless as required during the Sabbatical Year. In that case, the am ha’aretz who gathered the produce is paid only for the act of harvesting and not for the produce. However, if he buys produce that came from a field that was safeguarded for its owner in the manner that it is during the other years of the Sabbatical-Year cycle and was not declared ownerless, then even if one purchased produce worth half an issar, it is prohibited to transfer the money to him, as it is prohibited to utilize fruits that were safeguarded during the Sabbatical Year.

מתיב רב ששת: ומן המופקר שלש סעודות ותו לא? ורמינהי: הפיגם והירבוזין והשיטים וחלגלוגות והכוסבר שבהרים והכרפס שבנהרות והגרגיר של אפר ⁠— פטורין מן המעשר, וניקחין מכל אדם בשביעית, לפי שאין כיוצא בהן נשמר.

Rav Sheshet raised an objection: And is it permitted to purchase produce from an ownerless field worth only the value of 3 meals and no more? He raised a contradiction from a Mishnah (Shevi’it 9:1): Rue and sorrel, two types of herbs, and vegetables such as asparagus, purslane, coriander that is found in the mountains, water parsley of the rivers, and garden-eruca are all exempt from the requirement of tithes in all years, and they may be purchased from any person during the Sabbatical Year because there is no plant of their species that is safeguarded. These plants are not cultivated but grow wild, rendering them ownerless. Apparently, these plants that grow wild may be purchased in any quantity, even from an am ha’aretz, with no 3-meal limit.