Baraisa (Rabban Shimon ben Gamliel): If the messenger switched the sender's coin with his own coin, the messenger must tithe (as he has become the owner).

(R. Yosi): We learn from here that if a person gave money to his friend to be an unpaid watchman and the friend switched it and then lost it, he is liable.

(Shmuel): (The Mishnah (Menachos 10-1(b)) taught that if he said "This one is for me and that one is for my friend'' and they became mixed up, the Chaver must tithe them) He must only tithe when he took his portion for himself and gave the Am HaAretz his portion; but if the Am HaAretz came and took it, we say that he took his own portion and the Chaver is exempt from tithing.

(R. Eliezer): He must only tithe if he first gave the Am HaAretz his portion and then afterwards took his own.

(R. Yona): Both of these conditions are needed to require him to tithe the produce of the Am HaAretz - giving the produce to the Am HaAretz and taking his own portion second.

Baraisa: A person may say to his laborer - "Take this Dinar and buy food or drink for yourself'' and we aren't concerned that the laborer will buy produce of Shevi'is, untithed produce or Yayin Nesech. But if he told him, "Go out and buy for yourself a loaf or wine and I will reimburse you'', we are concerned.

(R. Zeira): (The Amoraim dispute why it is prohibited) (Until he has received his payment) the shopkeeper becomes like the messenger of the boss to give to the laborer.

(R. Hila disagrees): (Since the boss pays,) the food first becomes the property of the boss and the laborer then acquires it from him (so the boss is feeding him something prohibited).

Question: Where is there a practical difference between these two opinions?

Answer: If the shopkeeper was a deaf/mute - according to R. Zeira, there is no concern since a deaf/mute cannot act as a messenger. According to R. Hila, there is still a concern.

(Tosefta): A person shouldn't tell his (Am HaAretz) friend, "Take this 200 Dinars and buy produce and use it to pay the King's tax''. (We are concerned that he will buy Tevel (untithed) produce and one may not pay a debt with Tevel. Rather, he should say, "Pay my debt and I will reimburse you''.

Similarly, he shouldn't tell him, "Take this 200 Zuz and buy produce and pay the craftsman for his work''. Rather, he should say, "Pay the craftsman and I will reimburse you''.