Manava Dharmashastra 2.150

2.150

brahmagrahaṇārthaṃ janma brāhmam upanayanam, tasya kartā | svadharmasya śāsitā upadeṣṭā, vedārthavyākhyānena | sa tādṛśo bālo'pi brāhmaṇo vṛddhasya jyeṣṭhasya pitā bhavati | pitṛtulyā tatra vṛttiḥ kartavyā jyeṣṭhenāpi | “kathaṃ punaḥ kanīyāñjyeṣṭhamupanayate | aṣṭame hyupanayanam | yāvacca nādhītaśrutavedastāvannācāryakaraṇavidhāvadhikriyate |” evaṃ tarhi nopanayanamatra ‘brāhmaṃ janma’, kiṃ tarhi svādhyāyagrahaṇameva | tasya kartā'dhyāpayitā | svadharmasya vedārthasya śāsitā vyākhyātā pitā bhavati | dharmataḥ pitṛdharmāstatra kartavyāḥ | dharmata iti dharmanimittaṃ tatra pitṛtvam | na ca te dharmā adhyāpakavyākhyātroḥ pitṛsambandhinaḥ siddhāḥ santi, ato vidhīyante-brāhmaṇavatkṣatriye vartitavyamiti yathā |

The Brāhmaṇa, who brings about his Vedic birth, and teaches him his duty,—even though he be a mere child,—becomes in law the father of the old man (whom he teaches).—(150)

Medhātithi’s commentary (manubhāṣya):
The ‘birth’ that is for the purpose of getting up the Veda is called ‘Vedic birth,’—i.e., the Initiatory Rite.—He who brings about this; and ‘he who teaches him his duty—instructs him in it, by expounding the meaning of Vedic texts,—such a Brāhmaṇa,—‘even though he be a child.’—becomes tho father of the old man. That is, even though the pupil be older in age, he should treat the teacher as his father.

Question.—“How can the younger man ‘initiate’ the older? Specially as initiation is performed in the eighth year; and until one has duly learnt and studied the Veda, he is not entitled to act up to the injunction of ‘becoming a teacher.’”

Answer.—Well, in that case, we can take the term ‘Vedic birth’ to mean not necessarily the Initiatory Ṛte, but only the getting up of the Veda. One who ‘brings about’ this—i.e., the Teacher,—and ‘he who teaches’—expounds—‘him his duty’—i. e., the meaning of the Vedic texts,—‘becomes his father.’

‘In law;’—this means that the treatment of the father should be accorded to him; so that what the phrase ‘in law’ means is that the parental character of the teacher is based upon the treatment accorded to him. The ‘treatment of the father’ has not yet been declared as to be accorded to the teacher and the expounder; hence it has been laid down here; in the same manner as the injunction that ‘the Kṣatriya should be treated as the Brāhmaṇa.’—(150)

This verse is quoted in Madanapārijāta (p. 31);—in Parāśaramādhava (Ācāra, p. 305) in support of the view that when a boy teaches an old man, the former is his superior;—and in Vīramitrodaya (Saṃskāra, p. 480).

Comparative notes by various authors
(verse 150-154)
Baudhāyana-Dharmasūtra, 2-48.—‘This is found in the case of the infant Āṅgirasa.’

Sūtasaṃhitā, 6-31.—‘To regard the Teacher as a child or a human being or an uncultured person,—is the result of ignorance.’

Gautama-Dharmasūtra, 6.22-23.—‘Learning is superior to all; since it forms the very basis of Dharma.’

Viṣṇu-smṛti (Parāśaramādhava, p. 305).—‘One should behave towards the Teacher,—be he a child or of the same age as oneself,—as towards the Guru.’