Manava Dharmashastra 11.126

11.126

turīyo brahmahatyāyāḥ kṣatriyasya vadhe smṛtaḥ
vaiśye 'ṣṭamāṃśo vṛttasthe śūdre jñeyas tu ṣoḍaśaḥ //

As atonement for deeds which degrade to a mixed caste (Samkara), and for those which make a man unworthy to receive gifts (Apatra), (he shall perform) the lunar (penance) during a month; for (acts) which render impure (Malinikaraniya) he shall scald himself during three days with (hot) barley-gruel.