Gobhilagrihyasutra 1.6

Thus has spoken Mânatantavya: 'Unoffered indeed becomes the offering of a man who does not eat fast-day food.

'He becomes powerless. Hunger will attack him. He does not gain favour among people. His offspring will be perverse.

'But he who eats fast-day food, becomes powerful. Hunger will not attack him. He gains favour among people. His offspring will be still more blessed.

'Therefore (husband and wife) should eat fast-day food which is pleasant to them.'

Let them sleep that night on the ground.

They should spend that night so as to alternate their sleep with waking, entertaining themselves with tales or with other discourse.

But they should avoid doing anything unholy (such as cohabiting together).

It is said, that when on a journey, he should not fast.

For (say they, in that case) the observance has to be kept by his wife.

Let him do (herein) what he likes.

In the same way also one who has set up the (Srauta) fires should fast—

And (he should observe) what is enjoined by the sacred tradition.

Now in the forenoon, after (the sacrificer) has offered his morning oblation, and has walked round the fire on its front side, and strewn to the south of the fire eastward-pointed Darbha grass—

(The Brahman) stations himself to the east of that (grass), facing the west, and with the thumb and the fourth finger of his left hand he takes one grass blade from the Brahman's seat and throws it away to the south-west, in the intermediate direction (between south and west), with (the words), 'Away has been thrown the dispeller of wealth.'

Having touched water, he then sits down on the Brahman's seat, with (the words), 'I sit down on the seat of wealth.'

Facing the fire he sits silently, raising his joined hands, till the end of the ceremony.

Let him speak (only) what refers to the due performance of the sacrifice.

Let him not speak what is unworthy of the sacrifice.

If he has spoken what is unworthy of the sacrifice, let him murmur a verse, or a Yagus, sacred to Vishnu.

Or let him only say, 'Adoration to Vishnu!'

If one wishes, however, to do himself the work both of the Hotri and of the Brahman, he should in the same way place on the Brahman's seat a parasol, or an outer garment, or a water-pot, or a bolster of Darbha grass, and should return in the same way (in which he has gone to the Brahman's seat), and then should perform the other (duties).