Gobhilagrihyasutra 3.4.24

3.4.24

brāhmanān bhojayitvā, svayaṃ bhuktvā keśa-śmaśru-roma-nakhāni vāpayīta śikhāvarjam.

After he has entertained the Brâhmanas with food and has eaten himself, he should have his hair, his beard, the hair of his body, and his nails cut, so as to leave the lock of hair (as required by the custom of his family).