Related על תרומות 9:7

One who pulls weeds among [terumah] leeks with a Gentile (alt., "with a Samaritan"), even though its produce is untithed, he may not* eat casually among the produce [of leeks]. [*Note: Ter. 9:7 has "he may eat casually."] Rabbi Shimon ben Elazar says, right after shevi'it (the seventh year of the agricultural cycle, when fields lie fallow), he is permitted [to eat casually if he is weeding alongside] a Jew.