Manava Dharmashastra 2.148

2.148

ācāryāttu yattasya janma tadavināśi | gṛhīte vede'vagate ca tadarthe karmānuṣṭhānātsvargāpavargaprāptirityasya sarvasyācāryamūlatvātsa śreṣṭhaḥ | yāṃ jātimutpādayati yaṃ saṃskāramupanayanākhyaṃ dvitīyaṃ janmeti janmasaṃstutiṃ nirvartayati, sāvitryā tadanuvacanena sā jātiḥ satyā sā'jarāmarā | yadyapyete'bhinnārthāḥ śabdāstathāpīhopanayanākhyasya janmano mātṛjanmanaḥ sakāśādutkarṣātiśayavivakṣāyāṃ prayuktāḥ | na hi jarāmṛtyū prāṇināmiva jāteḥ sambhavataḥ | avināśitvaṃ tvekenaiva śabdena śakyate pratipādayitum | na ca tatpratipādyate | vedapāraga ācāryo yāṃ jātiṃ vidhivatsāvitryā upanayanāṅgakalāpena-sāvitrīśabdasya tallakṣaṇatvāt-utpādayati sā śreyasīti, padayojanā | jātirjanma |

But the “birth” which the Preceptor, well-versed in the Veda, brings about for him, in the lawful manner, by means of the Sāvitrī,—that is real, imperishable, immortal.—(148)

Medhātithi’s commentary (manubhāṣya):
The ‘birth’ that the Boy obtains from his Preceptor is however indestructible. When the Veda has been got up and its meaning duly comprehended, then alone is one enabled to perform religious acts, by which he obtains Heaven and Final Release; and since all this is due to the Preceptor, he is superior.

‘That birth which the Preceptor brings about’—i.e., the sacramental rite called ‘Upanayana’ ‘initiation,’ which is called the ‘second birth,’ which he accomplishes—‘by means of the Sāvitrī’—i.e., by the expounding of it;—‘that’—birth—‘imperishable, immortal.’ Though all these words mean the same thing, yet they have been used with a view to pointing out that the ‘birth’ named ‘Initiation’ is superior to that which one obtains from his mother. As a matter of fact, ‘perishing’ and ‘death’ are not possible for ‘birth,’ as they are in the case of living beings; if mere ‘indestructibility’ were meant, this could have been expressed by means of a single word; and yet this is not what is done (which shows that the meaning is as explained above).

The construction of the sentence is as follows:—‘Vedapāraga ācāryo yāñjātim vidhivat sāvitryā—i.e., by means of the full details of the Initiatory Rite, which is what is indicated by the term sāvitrī—utpādayati—is what is superior.’ ‘Jāti’ stands for ‘janma,’ birth.—(148)

It is also simply quoted in Vīramitrodaya (Saṃskāra, p. 480).

Comparative notes by various authors
Viṣṇu-smṛti, 30.5.—(Reproduces Manu.)

Āpastamba-Dharmasūtra, 1.1-17.—‘That is the highest birth; therein he gives him birth in knowledge.’

Gautama Dharmasūtra, 1.10.—‘That is the second birth.’