Atri Smriti 5.10

5.10

ubhāvetāvabhojyānnau bhuktvā cāndrāyaṇaṃ caret
amṛtaṃ brāhmaṇasyānnaṃ kṣatriyānnaṃ payaḥ smṛtam

both of these are persons whose food is inedible; having eaten it, one must perform the lunar penance; / a brahmin's food is considered nectar; a Kṣatriya's food is considered milk;