Manava Dharmashastra 4.40

4.40

pramattaḥ kāmaśaraiḥ pīḍito'pi | ārtavaṃ strīliṅgaśoṇitaṃ māsi māsi prasiddham | taddarśane na gacchet | ekasyāṃ ca śayyāyāṃ tayā saha na śayīta |
"sparśapratiṣedhādeva tatsiddhamiti" cet, nāyaṃ pratiṣedhaḥ | vrataṃmidaṃ, prāyaścittabhedaśca |

Even though mad, he shall not approach a woman during her courses; nor shall he sleep on the same bed with her.—(40)

Medhātithi’s commentary (manubhāṣya):
‘Mad’—even though suffering from the darts of passion.

‘Courses’—stands for the blood that appears every month in the woman. When this is visible, he shall not approach her. Nor shall he sleep on the same bed with her.

It may be argued that—‘the prohibition put forward is already implied in the aforesaid prohibtion of touching a woman in her courses.’

But what the present text contains is not a prohibition) but the injunction of a positive observance. And there is a difference in the expiatory rite prescribed in connection with the omission of this observance.—(40)

This verse is quoted in Vīramitrodaya (Āhnika, p. 562);—in Hemādri (Kāla, p. 726);—and in Nṛsiṃhaprasāda (Saṃskāra, p. 25a).

Comparative notes by various authors
(verses 4.40-42)
Gautama (9.30-31).—‘Not when she is in her courses;—nor shall he embrace her in this condition.’

Vaśiṣṭha (12.4).—‘He shall not associate with a woman with dirty clothes: nor with one in her courses; nor with one who is unfit.’

Viṣṇu (69.11).—‘Not when she is impure.’

Gobhila (3.5.5).—‘Not when she is in her courses.’

Bṛhannāradīya (28, 87-88).—‘If one touch a woman in her courses, or a Cāṇḍāla, or one who has committed a heinous crime, or a newly delivered woman, or the leavings of food, or the washerman and such others,—he shall bathe forthwith with his clothes on, etc., etc.’

Viṣṇupurāṇa (Vīramitrodaya-Āhnika, p. 562).—‘One shall not approach his wife before she has bathed or when she is ill, or in her courses.’