Vaishnava Dharmashastra 55.2

55.2

sravantīm āsādya snātaḥ pratyahaṃ ṣoḍaśa prāṇāyāmān salakṣaṇān kṛtvaikakālaṃ haviṣyāśī māsena brahmahā pūto bhavati ||

The killer of a Brâhmana is purified, if, having approached a river (and bathed in it), he restrains his breath sixteen times, and takes only one meal, consisting of food fit for offerings, each day, for a month.