Relationships Between "Religious" and "Secular" Jews - Mishnah Demai

Those who take it upon themselves to be trustworthy (ne’eman), must tithe whatever they eat and whatever they sell and whatever they buy, and they may not be the guest of an am haaretz.

Rabbi Judah says: even one who is the guest of an am haaretz can still be considered trustworthy.

They said to him: He is not trustworthy with himself! How can he be considered trustworthy with others?

One who takes it upon himself to become a chaver may not sell to an am haaretz either wet or dry produce, nor buy from him wet produce, nor be the guest of an am haaretz, nor host an am haaretz as a guest while he is wearing his cloak.

Rabbi Judah says: [a chaver] may not also raise small animals, nor make a lot of vows, nor joke around too much, nor become defiled by contact with the dead. Rather, [a chaver] should be an attendant at the house of study.

They said to him: these practices do not come within the general rule [of being a chaver].

One who vowed to have his friend eat with him - but the friend does not trust him with tithes - he may eat with him on the first Shabbat even though he does not generally trust him with tithes, provided that his friend said to him that the food had been tithed.

But on the second Shabbat, even if he has vowed, [the chaver] may not eat with him unless he first tithes the produce.

Someone enters a city and doesn’t know anyone. So they say: “Who here is trustworthy? Who gives tithes here?” One person one responds: “I am.” That person may not be trusted. [But if] that person replied: “So-and-so is trustworthy,” then so-and-so may be trusted.

If they then went to buy from so-and-so, and asked so-and-so: “Who here sells aged produce?” and so-and-so replies: “The one who sent you to me,” though they appear to be repaying each other, they may be trusted.