Tosefta su Levitico 19:24

A Jewish Priest [can] eat with a Samaritan Priest when [the food is] made in [a state of] impurity, but when [it is] made in [a state of] purity, behold, he does not eat it with him, because he feeds him the meat of an unblemished first-born [calf], and has him drink wine from a [ritually] pure fourth[-year vineyard]. [See Deut. 15:22 and Lev. 19:24, and discussions at Bekh. 5:2 (also Bekh. 32b:10) re: first-born calf, and Ter. 3:9 and Y. Peah VII.5.2 re: fourth-year vineyard.]

A Gentile who was shouting, and said "Come and buy for yourselves! This is produce from newly broken land (=עזק, see Jastrow)! This is uncircumcised fruit (Lev. 19:23)! This is fourth-year fruit (Lev. 19:24)!" he is not to be trusted, because he is like one who praises [מקחו], but if he says "This is from such-and-such Samaritan," [or] "I bought this from such-and-such Gentile," [or] "This comes from my own," he is trusted to be stringent, the words of Rebbi. Rabban Shimon ben Gamaliel says, "We do not trust him, as the words of a Gentile make no difference (lit., do not go up and do not go down)."