3,443. The Legislation of Demai

Hilchos Maaser 9:1

In the time of Yochanan the Kohein Gadol, who succeeded Shimon HaTzaddik, the Sanhedrin sent messengers throughout the land of Israel who determined that everyone was careful with terumah gedolah and would separate it, but unlearned people were not careful when it came to first tithe, second tithe and the tithe for the needy. They therefore ruled that only trustworthy people (defined in the next chapter) would be relied upon when it comes to tithes. The unlearned masses are considered doubtful in this matter. If they say that they took tithes, the produce is called demai (doubtfully tithed).

Hilchos Maaser 9:2

The Sages rules that one need only take terumas maaser and second tithe from doubtfully tithed produce (demai). This is because the former is a capital offense, while there’s no loss to the owner in separating the latter since he can eat it himself. One need not take first tithe or the tithe for the needy from demai because there’s a doubt and if one wants to take property from another person, the burden of proof is on the one requesting it to prove that it’s owed. Therefore, the owner of demai can tells the Levite or the needy person to bring proof that the produce is untithed; if he does so, then he can have the tithes.