Tosefta zu Bekhorot 5:11

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.]