Hiranyakeshigrihyasutra 1.2.8

He keeps through three days the (following) vow:

He eats no pungent or saline food and no vegetables; he sleeps on the ground; he does not drink out of an earthen vessel; he does not give the remnants of his food to a Sûdra; he does not eat honey or meat; he does not sleep in the daytime; in the morning and in the evening he brings (to his teacher) the food which he has received as alms and a pot of water; every day (he fetches) a bundle of firewood; in the morning and in the evening, or daily in the evening he puts fuel on (the fire, in the following way):

Before sprinkling (water) round (the fire), he wipes (with his wet hand) from left to right round (the fire) with the verse, 'As you have loosed, O Vasus, the buffalo-cow' (Taitt. Samh. IV, 7, 15, 7), and sprinkles (water) round (the fire) as above.

(Then) he puts (four) pieces of wood (on the fire) with the single (Vyâhritis) and with (the three Vyâhritis) together, and (four other pieces) with (the following four verses),
'This fuel is thine, Agni; thereby thou shalt grow and gain vigour. And may we grow and gain vigour. Svâhâ!
'May Indra give me insight; may Sarasvatî, the goddess, (give) insight; may both Asvins, wreathed with lotus, bestow insight on me. Svâhâ!
'The insight that dwells with the Apsaras, the mind that dwells with the Gandharvas, the divine insight and that which is born from men: may that insight, the fragrant one, rejoice in me! Svâhâ!
'May insight, the fragrant one, that assumes all shapes, the gold-coloured, mobile one, come to me. Rich in sap, swelling with milk, may she, insight, the lovely-faced one, rejoice in me! Svâhâ!'

Having wiped round (the fire) in the same way, he sprinkles (water) round (the fire) as above.

He worships the fire with the Mantras, 'What thy splendour is, Agni, may I thereby' (Taitt. Samh. III, 5, 3, 2), and 'On me may insight, on me offspring' (Taitt. Âranyaka X, 44).

After the lapse of those three days (Sûtra 1) he serves in the same way the three kinds of food (stated above) to the Brâhmanas, causes them to say, 'An auspicious day! Hail! Good luck!' and discharges himself of his vow by (repeating) these (Mantras) with (the necessary) alterations, 'Agni, lord of the vow, I have kept the vow' (see above, I, 2, 7, 8).

He keeps the same observances afterwards (also),

Dwelling in his teacher's house. He may eat, (however,) pungent and saline food and vegetables.

He wears a staff, has his hair tied in one knot, and wears a girdle,

Or he may tie the lock on the crown of the head in a knot.

He wears (an upper garment) dyed with red Loth, or the skin (of an antelope, &c.).

He does not have intercourse with women.

(The studentship lasts) forty-eight years, or twenty-four (years), or twelve (years), or until he has learnt (the Veda).

He should not, however, omit keeping the observances.

At the beginning and on the completion of the study of a Kânda (of the Black Yagur-veda he sacrifices) with (the verse), 'The lord of the seat, the wonderful one, the friend of Indra, the dear one, I have entreated for the gift of insight. Svâhâ!'
In the second place the Rishi of the Kânda (receives an oblation).
(Then follow oblations with the verses), 'This, O Varuna;' 'For this I entreat thee;' 'Thou, Agni;' 'Thus thou, Agni;' 'Thou, Agni, art quick;' 'Pragâpati!' and, 'What I have done too much in this sacrifice.' Here some add as subordinate oblations the Gaya, Abhyâtâna, and Râshtrabhrit (oblations) as above.
End of the Second Patala.