Manava Dharmashastra 11.129

11.129

etad eva cared abdaṃ prāyaścittaṃ dvijottamaḥ
pramāpya vaiśyaṃ vṛttasthaṃ dadyāc gavām //

Or he may perform the penance prescribed for the murderer of a Brahmana during three years, controlling himself, wearing his hair in braids, staying far away from the village, and dwelling at the root of a tree.