मातुर्यदग्रे जायन्ते द्वितीयं मौञ्जिबन्धनात् ।
ब्राह्मणक्षत्रियविशस्तस्मादेते द्विजाः स्मृताः ॥
mātur yad agre jāyante dvitīyaṁ mauñji-bandhanāt |
brāhmaṇa-kṣatriya-viśas tasmād ete dvijāḥ smṛtāḥ ||
(Yājñavalkya Smṛti: 1.39)
“Since they are born first from a mother [i.e., by way of seminal birth] and second by the tying of mauñji [i.e., the upanayana-saṁskāra, which involves a ritual in which mauñji, a type of cane grass, is tied as a girdle around the initiate’s waist], these brāhmaṇas, kṣatriyas, and vaiśyas are known as the twice-born (dvijas).”