3,456. Selling Produce in Large Volumes

Hilchos Maaser 11:1

One may not sell demai to an unlearned person, nor send it as a gift, because by doing so one would be assisting him in eating something prohibited. Demai may be sold or sent to a Torah scholar because such a person won’t eat it until tithing it or hearing from someone trustworthy that it was tithed.

Hilchos Maaser 11:2

Anyone who adds to the volume of produce they sell in large amounts, like wholesale vendors and grain merchants, may sell demai and send it as a gift. Since they add to it, the Sages ruled that the buyer or recipient take the tithes. However, those vendors who only use small measures must take the tithes themselves because they’re the ones who are profiting. Therefore, small vendors may not sell or send demai unless it has first been rectified.