Rāmānujaon Brahma Sūtra 1.3.37a

The Sûdra is specially forbidden to hear and study the Veda and to perform the things enjoined in it. 'For a Sûdra is like a cemetery, therefore the Veda must not be read in the vicinity of a Sûdra;' 'Therefore the Sûdra is like a beast, unfit for sacrifices.' And he who does not hear the Veda recited cannot learn it so as to understand and perform what the Veda enjoins. The prohibition of hearing thus implies the prohibition of understanding and whatever depends on it.