Agniveshyagrihyasutra 1.1.1.1

1.1.1.1

upanayanaṃ vyākhyāsyāmaḥ saptame varṣe brāhmaṇamupanayītaikādaśavarṣe rājanyaṃ dvādaśe varṣe vaiśyam \

We shall explain the initiatory investiture. One should invest a Brahmin in the seventh year, a Kṣatriya in the eleventh year, [and] a Vaiśya in the twelfth year.