Demai 4:6-7

Demai 4:6

If a stranger in town asks who can be relied upon to separate tithes and someone replies, “I am,” that person is not believed (because one cannot vouch for himself). If he names another person, he can be believed. If the stranger went to buy from that person and he asks, “Who sells yoshon* here?” and the seller names the one who referred the stranger, they may both be believed even though it appears that they are cross-promoting one another’s businesses.

*Referring to grain of the previous harvest, as opposed to chadash, which may not be eaten before the Omer was brought.

Demai 4:7

If donkey drivers enter a city and one of them says, “My produce is chadash but my friend’s is yoshon” or “my produce is untithed but my friend’s is tithed,” they are not believed (because they appear to be in cahoots). Rabbi Yehuda says they are believed (because if we don’t buy from them, vendors will stop coming to town).