Manava Dharmashastra 4.76

4.76

ādikarmaṇi vidhimimaṃ samācaret | ārdrapādo bhojanamācaret | na cātṛpteḥ pādau siñcannāsīta | saṃviśet | śayane gātrāṇi nāvakṣipet | saṃveśanaṃ śayane gātrasaṃyojanam | asya phalamāha | dīrghamāyuriti | nāyamāyuṣkāmasya vidhiḥ-kintarhipūrvavannityaḥ | āyuranuvādastvarthavāda eva |

He shall eat with wet feet; but he shall not sleep with his feet wet. By eating with wet feet, one would attain long life.—(176)

Medhātithi’s commentary (manubhāṣya):
Before the act of eating, one shall observe the rule that ‘one should eat with wet feet;’ it is not meant that he should go on wetting his feet till he has finished eating and become fully satisfied.

‘Shall not deep’—i.e., he shall not lay down his body upon the bed; ‘samveśana,’ ‘sleeping,’ standing for the laying down of the body on the bed.

The reason for this is next mentioned—‘Long life.’—It does not mean that the injunction is meant only for one who desires long life (and for none others); in fact, like the preceding ones, this also is obligatory; and the mention of ‘long life’ is purely illustrative.—(76)

This verse is quoted in Saṃskāramayūkha (p. 72).

Comparative notes by various authors
Mahābhārata (12.191.6-7).—‘He shall eat food with five limbs wet,—facing the east and silent; he shall not decry the food, he should cat it whether it be tasty or otherwise. He shall not rise from his seat with wet hands. He shall not sleep with wet feet.’

Do. (13.104.61).—[Reproduces Manu.]

Viṣṇu (69.34).—‘Nor with unwet feet, nor with unwet hands and mouth (shall he eat).’

Viṣṇu (70.1).—‘He shall not sleep with wet feet.’