Manava Dharmashastra 2.181

2.181

kāmādvratalopenāvakirṇiprāyaścittam, akāmātvidamāha | svapnagrahaṇamavivakṣitam, akāmata ityetadeva nimittam | na hi svapne kāmasambhavaḥ | ato yadyasuptasyāpi kathañcidanikṣayā svamalāsṛgavayavavatprakṣarati śuknaṃ tatrāpyetadeva prāyaścittam | akāmato retaḥ siktavedaṃ prāyaścittaṃ kuryāt-punarmāmiti ṛcaṃ japet |

The twice-born religious student, haying unintentionally dropped his manhood during a dream, should thrice recite the three vedic verses beginning with “punarmām,” after having bathed and worshipped the sun.—(181)

Medhātithi’s commentary (manubhāṣya):
When one renounces his vow of continence intentionally, then he has to perform the expiatory rite prescribed for the ‘Avakīrṇī’ (11.120 et. seq.); the present verse lays down what one should do when he does it unintentionally.

No significance attaches to the mention of ‘dream’; the absence of intention is the only necessary condition; and no intention can be present during dreams. Hence this same expiatory rite is to be performed in a case where, even though he may be not asleep, the flow occurs involuntarily, in the same manner as certain other fluids flow out of the body.

The sense of the verse thus is that—‘if one drops his manhood unintentionally, he should perform this expiatory rite that he should recite the three verses, etc., etc.—(181)

‘Punarmām’—“This verse occurs in Taittirīya Āraṇyaka 1. 30,”—Buhler.

Punarmāmaitvindriyam—Taittirīya Āraṇyaka 1. 30. Such uses of texts are frequent in the later Vedic works; e.g. the Sāmavidhāna Brāhmaṇa and the several Ṛgvidhānas,”—Burnell.

This verse is quoted in Parāśatramādhava (Prāyaścitta, p. 394), as laying down what should be done by the Religious Student, in the event of a ‘wet dream—in Madanapārijāta (p. 39);—in Aparārka (p. 1141);—in Smṛticandrikā (Saṃskāra, p. 127) as showing that unintentional emission involves only an expiation;—and in Prāyoscittaviveka (p. 462).

Comparative notes by various authors
Yama (Aparārka, 11.41).—‘The Religious Student involuntarily emitting semen during a dream shall bathe, look at the Sun and repeat the Gāyatrī a hundred and eight times.’

Viṣṇu (28.53)—(reproduces Manu’s words).