Manava Dharmashastra 5.64

5.64

pitṛmedhaḥ parameṣṭiḥ | anye tu sarvaṃ karmaiva lakṣyata iti prāhuḥ | tatkurvan śiṣyo daśarātreṇa śudhyati | brahmacāriṇo'pyayaṃ vidhirastyeva | pretāhāraiḥ samaḥ | pretaṃ haranti niryāpayanti tathā teṣāṃ daśāhaḥ | evaṃ śiṣyasyāpītyarthaḥ |

The pupil performing the ‘Pitṛmedha’ for his dead Teacher becomes purified in ten days; just as those who carry the dead body.—(64)

Medhātithi’s commentary (manubhāṣya):
‘Pitṛmedha’— i.e., the final sacrificial offering; others hold that the term stands for the entire procedure (of the Śrāddha);—performing this, the pupil becomes purified in ten days. This same rule applies to the Student also.

‘Just as those who carry the dead body’;—for those who take out the dead body, the period is ten days; and so it is for the pupil also.—(64).

(Verse 65 of other commentators.)

‘Pitṛmedha’—The Antyeṣṭi (Medhātithi, Govindarāja, Kullūka and Rāghavānanda);—‘the entire Śrāddha ceremony’ (‘others’ noted by Medhātithi).

This verse is quoted in Aparārka (p. 912), which says that the ‘guru’ meant here is Ācārya, and that ‘Pitṛmedha’ is Antyeṣṭi;—in Mitākṣarā (on 3.24), to the effect that if the pupil performs Antyeṣṭi of his guru, then he is to be impure for ten days;—in Nirṇayasindhu (p. 381) as reiterating the ‘ten-day’ period for all carriers of the dead body, the ‘pupil’ being mentioned only by way of illustration.

Comparative notes by various authors
Viṣṇu (22.85).—(Same as Manu.)

Āśvalāyana Gṛhyasūtra (4.4.19).—‘Ten days after the death of a Guru who is nut a Sapiṇḍa.’

Yājñavalkya (3.24).—‘In the case of the Guru, the disciple, the Expounder of the Veda, the maternal uncle and the Vedic Scholar,—there is purification in a single day.’

Bṛhaspati (Aparārka, p. 913).—‘For three days one remains impure, on the death of the maternal grandfather, the Ācārya and the Vedic Scholar.’

Uśanas (Aparārka, p. 913).—‘On the death of the maternal uncle, the Father-in-law, the friend, the Guru and the Guru’s wife, and the maternal grandmother, one is impure for a night along with the clay preceding and following it.’