Tosefta על פאה 8:3

Rabbi Yehudah says, [with respect to] a place (i.e., a vineyard) that typically produces Olelet (defective clusters), a poor person [selling wine in a location near the vineyard] is believed to say, "This wine is from Olelet" and that he gathered it as part of his gathering. [If he said,] "I and my brother," or "I and my close relative [gathered these grapes]" [he is also believed], but he is not believed to say "From such-and-such Gentile I bought it," [or] "From such-and-such a Samaritan man I bought it." The poor among the Samaritans are like the poor among the Jews [in this respect], but the poor among the Gentiles are not believed in any matter.