Terumot, Chapter One, Mishnah Two
Our mishnah clarifies the meaning of heresh which I translated in yesterdays mishnah to mean deaf-mute.
1) A heresh, who speaks but cannot hear, may not give terumah, but if he does so, his terumah is terumah.
2) The heresh of whom the sages generally speak is one who neither hears nor speaks.
Section one: In yesterdays mishnah we learned that if a heresh separates terumah, his terumah is not terumah. Here we learn that mishnah one referred only to the typical type of heresh, one who neither speaks nor hears. However, if the heresh can speak but not hear then he still may not give terumah but if he does so, it is valid. The Talmud explains that he shouldnt give terumah because he cannot hear the blessing. His terumah is valid because if he can communicate, then we know that he has daat (legal cognizance of his actions.)
Section two: This section clarifies that generally when we talk about the heresh it refers to a deaf-mute and not to a deaf person who can speak. Assumedly a deaf person who could speak would almost always have been someone who went deaf later in life. A person who was born deaf would probably, in those days, never learn to speak.