Jewish Mothers of Chazal

How do we know that there were Jewish mothers influencing Chazal (our sages of blessed memory)?

Gemara: Chullin 105a. Mayim rishonim (the washing done before a meal) is a mitzva, while mayim acharonim (done after the meal) is an obligation. Rav Idi bar Avin reiterates that there are two reasons for washing the hands - one, because of terumah, two, because "it is a mitzvah."

As a mitzvah de rabbanan (from the rabbis), why is it a mitzvah?
Because it is a mitzvah de oraita (from the Tanakh) that you should honor your father and mother. And your mother says,

"Wash your hands before you eat!"