Vaishnava Dharmashastra 22.10

22.10

savarṇasyāśauce dvijo bhuktvā sravantīm āsādya tannimagnas triraghamarṣaṇaṃ japtvottīrya gāyatryaṣṭasahasraṃ japet ||

If a twice-born man has eaten (the food) of a member of his own caste, while the latter was impure, he must approach a river and plunge into it, mutter the (hymn of) Aghamarshana three times, and, after having emerged from the water, must mutter the Gâyatrî one thousand and eight times.