One may grind one’s tithed produce and deposit it with those who eat Sabbatical-Year produce and those who eat their own produce in a state of impurity, because there is no concern that they will exchange this produce with Sabbatical-Year produce or with impure produce, or that they will touch the produce. But one may not grind for those who eat Sabbatical-Year produce or for those who eat their own produce in a state of impurity, so as not to assist them in committing a transgression. This is difficult according to Rava’s explanation of the mishna, that the wife of a ḥaver may grind non-sacred produce with the wife of an am ha’aretz, who eats his own produce in a state of ritual impurity.

Abaye said: There, in that baraita, we are dealing with a priest who is suspected with regard to partaking of teruma in a state of ritual impurity, which involves a prohibition of impurity by Torah law.

The Gemara asks: If so, if the baraita is referring to a priest, how then may one deposit tithed produce with him? The Gemara raises a contradiction from that which was taught in a baraita (Tosefta, Demai 4:28): One may deposit teruma with an Israelite who is an am ha’aretz. Although he is not meticulous about the halakhot of purity, there is no concern that he will defile the teruma. But one may not deposit teruma with a priest who is an am ha’aretz because he is accustomed to having teruma, and therefore he might not treat it properly and will touch and defile it.

Rabbi Ile’a says: With what are we dealing here, in the previously mentioned baraita, which teaches that one may deposit his tithed produce with one who eats his own produce in a state of ritual purity? This is referring to a case where one deposited the produce in an earthenware vessel with a tightly bound cover. In such a case, there is no concern that the priest who is suspected of partaking of teruma in a state of ritual impurity will touch the produce and render it impure.

The Gemara asks: And let there nevertheless be a concern lest the priest’s menstruating wife move the vessel and impart ritual impurity to the produce inside it. A menstruating woman imparts impurity to the produce inside the vessel through moving it, even if the contents are tightly sealed in the vessel, and she does not come into direct contact with the contents.

Rather, Rabbi Yirmeya says that this is not difficult. Here, where it is prohibited to deposit produce with a priest who is suspected with regard to partaking of teruma in a state of ritual impurity, we are dealing with produce that came into contact with a liquid and became susceptible to contracting ritual impurity. Consequently, there is concern that the priest may impart impurity to it. There, where it is permitted to deposit produce with such a priest, we are dealing with produce that has not yet become susceptible to contracting ritual impurity, in which case there is no concern that the priest will impart impurity to it.

And the Gemara raises a contradiction from what is taught in a mishna (Demai 3:4): With regard to one who takes tithed wheat to a Samaritan grinder or to a grinder who is an am ha’aretz, the wheat retains its presumptive status with regard to tithes and Sabbatical-Year produce, as there is no concern that the grinder switched the grain. But the wheat does not retain its presumptive status with regard to impurity, as there is concern that perhaps the grinder touched it and rendered it impure.

The Gemara asks: What contradiction is there here? Did we not establish that the baraita that permits depositing produce is dealing with produce that has not yet become susceptible to contracting ritual impurity, and so it does not become impure when touched by an impure person? Here, the mishna in tractate Demai is dealing with produce that already became susceptible to contracting ritual impurity, and therefore there is concern that the produce will be rendered impure.

The Gemara asks: And he who asked the question, why did he ask it? Wasn’t this answer already stated earlier? The Gemara answers: The one who asked the question cited this mishna only because he wished to raise a contradiction to it from another mishna, as according to this mishna the wheat that was brought to the suspect grinder retains its presumptive status with regard to tithes and Sabbatical-Year produce, and we are not concerned that perhaps the grinder exchanged the grain he had received with grain of his own that was forbidden in some way.

And the Gemara raises a contradiction to this from what was taught in a mishna (Demai 3:6): With regard to one who gives food to his mother-in-law, who is the wife of an am ha’aretz, so that she may prepare it for him, he must tithe everything that he gives her and everything that he takes from her. This is because she is suspected of exchanging any food received from him that was spoiled with her own food that was not spoiled. Perhaps, then, she did not return the food that he had given her but rather food that was not yet tithed. In this mishna, there is concern that an am ha’aretz may exchange produce that he received with produce of his own.

The Gemara answers that there the concern is for the reason that was explicitly taught in that mishna: Rabbi Yehuda said: His mother-in-law wants what is good for her daughter, that she not eat anything that is spoiled, and she is ashamed before her son-in-law to tell him that he had given her something that was spoiled. For this reason, she does not tell him that she exchanged the food.

The Gemara asks: And is this to say that in the case of ordinary people we are not concerned that food will be exchanged in a similar situation? But didn’t we learn in a mishna (Demai 3:5): If one gives food to an innkeeper [pundakit] so that she can prepare it for him, he must tithe everything that he gives her and everything that he takes from her, because she exchanges the food received from him with food of her own? This indicates that the concern is not limited to the case of a mother-in-law. The Gemara answers: There, the innkeeper rules for herself that it is permitted for her to do this and says: Why should this student of Torah eat hot food while I will eat cold food? In other words, the innkeeper may justify her behavior to herself and exchange his food for hers.

The Gemara asks: And still, in the case of ordinary people, are we not concerned about food being switched? But isn’t it taught in a baraita (Tosefta, Teharot 8:4): The wife of a ḥaver may grind with the wife of an am ha’aretz when she, the wife of the ḥaver, is impure, e.g., when she is menstruating and therefore careful not to touch food. And there is no concern that she will come to eat untithed produce. But she may not do this when she is pure. Rabbi Shimon ben Elazar says: She may not grind even when she is impure, because the other woman, the wife of the am ha’aretz,