Tosefta su Salmi 121:4

A town that has in it Jews and Gentiles, guardians of Jews (see Psalms 121:4) and guardians of Gentiles, those who tithe and those who do not tithe, [or] guardians who tithe and guardians who do not tithe, they have the right to say, one to the other, "the north of the town is our portion and the south [of the town] is your portion." [But] if they started calculating (cf. Bava Batra 78b:13), it is forbidden [to say this, as perhaps it will appear that the division is motivated by pecuniary advantage rather than punctilious observance.]