(Mishnah): Five should not separate Terumah and even if they did, it does not take effect - a Cheresh (deaf-mute), a deranged person, a child and one who separates another person's produce.

If a gentile separated Terumah from a Yisrael's produce, even if it was with his consent, it is not Terumah.

A Cheresh who can speak but not hear should not separate Terumah, but if he did, it is valid. The standard Cheresh referred to by Chazal cannot hear or speak.

A child who does not yet have two pubic hairs - R. Yehuda says that his Terumah is valid Terumah; R. Yosi says - before he has reached the age of vows (which the Torah defines as within the year before his Bar Mitzvah, during which time his vows are valid as long as he understood what he was saying), his Terumah is not valid. Once he has reached the age of vows, it is valid.

(Gemara): 'Five should not separate Terumah etc.' R. Shmuel bar Nachman learned all of these from the following pasuk (Shemos 25:2), "Speak to the children of Yisrael and have them take for me an offering'' - this excludes a gentile; "from each man'' - this excludes a child; "whose heart inspires him'' - this excludes a Cheresh and a deranged person (who don't have sufficient understanding); (Pasuk 3) "And this is the offering you should take from them'' - this excludes one who separates another person's produce.

Question: (Even though a Cheresh and child don't have sufficient understanding) their action should prove their intent, as the Mishnah teaches (in Maseches Machshirin), 'If a Cheresh, imbecile or child took fruits onto the roof (so that the worms leave), even if they wanted dew to fall on them, they still cannot contract Tumah, since there is merely an action without intent (as their will is insignificant).

Which action was there (that indicated intent to get wet)? Rav Huna said that they held the fruit for the dew to fall on them....?

(Mishnah in Maseches Machshirin): If a Cheresh, imbecile, or child took an animal down to the river to drink, even if he intended it to wash its legs, it still cannot contract Tumah, since there is an action without clear intent.

Which action was there? Rav Huna said - rubbing the animal's legs in the water.

Conclusion of question: So too here, why doesn't the action of separating explain their intent and validate the Terumah?

Answer (R. Shmuel/ R. Abahu citing R. Yochanan/ R. Zeira citing Rabbanan): The pasuk states (Bamidbar 18:27), "And your Terumah shall be considered for you'' - since the pasuk refers to thought, his action does not prove his thought.

Question (R. Yosi to Shmuel): In the laws of Gittin, the pasuk doesn't refer to thought, but his actions still do not explain his thoughts, as the Mishnah taught (in Maseches Gittin), 'All may write a Get, even a Cheresh, a deranged person and a child' and Rav Huna explained that it is only when an adult is standing over them (and warning them to write it for the correct people)...?

Question (R. Yochanan to Rav Huna): How could an adult standing there help to give the correct intent to the Cheresh? (Their actions do not prove their intent. Rather, it is still invalid unless they left out the important parts to be written by an adult.) (This contradicts R. Yochanan's earlier statement (in (g)) that the actions prove intent as long as the Torah didn't specify that thought is needed...?)

Answer (R. Yosi himself to Shmuel): For a Get, the Cheresh etc. writes it and the husband divorces with it; but here (Terumah), the one who thought is the one who separated (i.e the child and one could have said that his intent is proven through this actions, so the Torah needed to write otherwise ("And you shall calculate'')).

(R. Yaakov bar Acha): If the one who wrote would be the one who divorces, it would be a valid Get. But for Terumah, even if the one who thought was the one who separated, the pasuk instructs us that his actions do not prove his intent.

(R. Yaakov bar Acha/ R. Chiya citing R. Yochanan): Some disagree with the Tanna of our Mishnah (who said that if a Cheresh, imbecile or child separate Terumah, it is invalid).

How is this? R. Yochanan of Terumos follows R. Yishmael son of R. Yochanan ben Beroka of Kidushin (i.e. adding the Parah Adumah ashes to the spring water) and R. Yochanan of Gitin follows the Rabbanan of Gitin (as we will see later on)...

(Tosefta in Maseches Parah): If a Cheresh, imbecile or child added the ashes, it is invalid. R. Yishmael, son of R. Yochanan ben Beroka, says that by themselves is not valid; but with others supervising, it is valid.