Demai 3:2: One who desires to trim leaves of vegetables in order to lighten his burden should not discard [the leaves] until he has tithed them. If one buys vegetables from the market and then decides to return them, he should not return them until he has tithed them, since they [the bundles] lack nothing but counting. However, if he is standing and selecting [the vegetables] and then sees another bundle that is of better quality he may put return them [without tithing] because he has not yet grasped them [in a manner of acquisition].

הרוצה לחזום עלי ירק להקל ממשאו לא ישליך עד שיעשר. הלוקח ירק מן השוק ונמלך להחזיר לא יחזיר עד שיעשר שאינו מחוסר אלא מנין. היה עומד ולוקח וראה טוען אחר יפה ממנו מותר להחזיר מפני שלא משך:

Demai 3:3: Someone who finds produce on the road, and takes them to eat them, but then decides to hide them, should not hide them until he tithes them. If from the start he took them [the produce] so that they should not spoil, they are exempt. Anything which a person is not permitted to sell when it is Demai should also not be sent to a friend when it is Demai. Rabbi Yossi allows this [in a case of] certainly [untithed produce], as long as he informs him.

המוצא פירות בדרך ונטלן לאוכלן ונמלך להצניע לא יצניע עד שיעשר. ואם מתחלה נטלן בשביל שלא יאבדו פטור. כל דבר שאין אדם רשאי למכרן דמאי לא ישלח לחברו דמאי. רבי יוסי מתיר בודאי ובלבד שיודיענו: