(Mishnah): One who told his messenger, "Go and separate for me Terumah'', he should separate according to the intent of the sender (meaning whether he is generous, average or miserly). If he doesn't know the sender's intent, he should separate the average amount, which is 1/50th.

If he gave 1/60th or 1/40th, it is valid. But if he tried to add even a small amount more than the intent of the owner, it is not valid.

One who wishes to give excess Terumah (how much may he give?)

(R. Eliezer): One in ten, like the amount of Terumas Maaser. If he gives more than that, he should make it Terumas Maaser for produce elsewhere.

(R. Yishmael): He may make up to half Chulin and half Terumah.

(R. Tarfon and R. Akiva): As long as some of it remains Chulin.

(Gemara) Question: We have only discussed when the sender explicitly told him to separate according to his intent; but if he merely knows the intent of the sender but he was told to follow it, what is the law?

Answer: (The latter part of our Mishnah taught) - 'if he doesn't know the sender's intent, he should separate the average amount, which is 1/50th'. But if he knew his intent, even if he didn't specify, it's as if he said it.

(R. Bun bar Kahana): The meaning of the teaching (above (b)) in our Mishnah is - One who intended to give 1 Se'ah and he gave 9/10th or 1&1/10th Se'ah, it is valid. But it does not mean that he separated 1/60th or 1/40th instead of 1/50th, as in such a case, he is causing the owner to lose more in the lesser case (1/40th) than he gains in the greater case (1/60th).

What's the case? When he usually gives 1/50th and the messenger gave 1/40th, he's caused a loss of 11/2 Kav. If the messenger gave 1/60th, the owner has gained a Kav. If so, why when he reduced it by more than 1/10th is it not Terumah (even though it was a difference of only a little over a Kav), but if he added more than 1/10th, it is not Terumah when he lost more than 11/2 Kav?

(R. Chanina, son of R. Hillel): When he intended to add, the owner allows up to 11/2 Kav extra; but if he intended to reduce, if he reduced only a Kav, the owner is particular, as he does not want to appear miserly.

Question (R. Chagai to R. Yosi): (The Mishnah taught that if the messenger tried to add even a small amount more than the intent of the owner, it is not valid.) A Mishnah (in Maseches Meilah) teaches that if the owner told the messenger, "Give the guests a piece of meat'' and the messenger told the guest, "Take two each'' and the guests ultimately took three each; all have transgressed Meilah. (The messenger is considered to have added to, rather than transgressed the owner's intent which would have voided the agency.) But in our Mishnah, if the messenger tried to add anything at all, he has transgressed and voided the agency?

Answer (R. Yosi to R. Chagai): There, after the first piece of meat, the agency has been completed. Here, where he separates for the entire pile at the same time, could you say that at a certain point, his agency is completed?

So how is it comparable to the Mishnah in Meilah? If there were two piles, one of which was tithed according to his wishes and one which was not; (the first pile's Terumah is valid and the second pile's is not).