Manava Dharmashastra 2.180

2.180

ekaḥ śayīta sarvatra na retaḥ skandayetkvacit, ayaunāvapi | yonau strīpratiṣedhādeva siddhatvāt | atrārthavādaḥ kāmāddhi skandayan | icchā'tra 'kāmaḥ' | hastavyāpārādinā, ayonau maithunena ca, retaḥ śuknaṃ skandayan kṣarayanhinasti nāśayati brahmacaryavratamātmanaḥ |

He should always sleep alone; nowhere should he allow his manhood to run out; by intentionally allowing his manhood to run out, hr breaks his vow.—(180)

Medhātithi’s commentary (manubhāṣya):
‘He should always sleep alone; nowhere should he allove his manhood to run out,’—i.e., not even outside; intercourse with women having been already prohibited.

Next follows a commendatory statement—‘Intentionally, etc.’ ‘Intention’ means wish...... By allowing his manhood to run—by any means—he ‘breaks’—destroys—‘his vow’ of studentship (continence).—(180)

This verse is quoted in Madanapārijāta (p. 39), which explains ‘Vratam’ as ‘brahmacharyam’;—in Vīramitrodaya (Saṃskāra, p. 496);—only the first half in Parāśaramādhava (Ācāra, p. 456);—in Nṛsiṃhaprasāda (Saṃskāra, p. 46b);—and in Smṛticandrikā (Saṃskāra, p. 127), which explains ‘vratam’ as the vow of Studentship;—unintentional emission involves only an expiation, and not a breach of the vow.

Comparative notes by various authors
Viṣṇu (28.48).—‘Those Vedic Scholars who know Dharma have declared that in the case of the Brāhmaṇa under vow of studentship, intentional emission is a transgression.’

Gobhila Gṛhyasūtra (2.26).—‘He should avoid giving vent to his organ.’

Yama (Vīramitrodaya-Saṃskāra, p. 496).—‘Sitting and sleeping on a couch and teeth-cleansing should be avoided; he should sleep alone, on kuśa-grass, and should never emit his semen anywhere.’