(14) You shall not insult the deaf, or place a stumbling block before the blind. You shall fear your God: I am the Eternal.

(1) Five may not give terumah, and if they do so, their terumah is not considered terumah:A heresh; a shoteh, and a katan, And the one who gives terumah from that which is not their own. If a non-Jew gave terumah from that which belongs to an Jew, even if it was with his permission, his terumah is not terumah.

(2) A heresh, who speaks but cannot hear, may not give terumah, but if he does so, his terumah is terumah. The heresh of whom the sages generally speak is one who neither hears nor speaks.

(8) A person that can hear but not speak, or speak but not hear, that person is like hearing people and can be included in a minyan. But if they neither hear nor speak, they are treated like a mentally incompetent person or a minor.

[The mishna taught:] Except for a heresh, a shoteh, and a katan..

This teaches that a heresh is similar to a mentally incompetent person and a minor: Just as a mentally incompetent person and a minor who are not bnei deah [of full mental capacity - lit. children of knowledge], so too the ḥeresh is not a bar deah.

And this is like what we learned in a mishna (Terumot 1:2): The heresh of whom the sages generally speak is one who neither hears nor speaks. So one who speaks but does not hear and one who hears but does not speak are obligated in mitzvot

We already learned this, as the Sages taught [in the Tosefta (Terumot 1:2)]: One who speaks but does not hear is deaf. One who hears but does not speak is mute. Both this one and that one are in the same legal category as those who can see and hear with regard to all matters.

Rav Kahana says in the name of Rav: A heresh who can speak through writing, may write and give a bill of divorce to his wife....

 The Gemara raises an objection from a baraita: "We may follow the signals, and gestures of a heresh, as well as his writing only for selling movable property, but not for bills of divorce."

This is a debate between earlier sages, as it was taught [in another baraita (Tosefta, Terumot 1:1)] that Rabban Shimon ben Gamliel said: What is the case of the heresh? One who was deaf from from birth. But if he could previously hear, but became deaf later, then he may write and sign.