उपनीय तु यः शिस्यं वेदमध्यापयेद्द्विजः ।
सकल्पं सरहस्यं च तमाचार्यं प्रचक्षते ॥
upanīya tu yaḥ śisyaṁ vedam adhyāpayed dvijaḥ |
sa-kalpaṁ sa-rahasyaṁ ca tam ācāryaṁ pracakṣate ||
(Manu Smṛti: 2.40)
“A twice-born, however, who can confer the upanayana saṁskāra and teach a disciple the Veda along with its rites and and its mysteries is called an ācārya.”