Kaushitakagrihyasutra 2.7: atha saptamaḥ khaṇḍaḥ

Now the assignment of observances.

Its ritual procedure is explained by the initiation.

He does not recite the Sāvitrī.

[It lasts] up to the giving of the staff, say some.

During the northern course of the sun, in the waxing fortnight, having observed chastity for a day and a night, the preceptor, eating no meat,

leaving out the fourteenth, the eighth, and the ninth [tithis],

and the first and last, according to some,

or on whatever other [tithi] he regards as auspicious with regard to the asterisms, on that he should assign the Śukriya vow of studenthood.

“Become a Śukriya student,” says the preceptor.

“May I become a Śukriya student,” says the other.

In this manner, for the subsequent [vows], whatever vow he may assign, he should indicate by the respective name of each.

He should practice chastity for three nights,

or twelve nights, or a year,

or as long as the guru thinks fit.

And [likewise] for the Godāna.

The Śākvara [vow], however, lasts for a year, and also the Māhāvratika and the Aupaniṣada.

When the period is complete and the vow of studenthood has been observed, the Veda ending with the Śayu and Cārhaspatya having been recited, when he intends to recite the secret text, one should know the fixed rule of time by the instruction [given before].

After he has eaten his morning meal,

in the afternoon, having offered an oblation in the invincible quarter, the preceptor then asks him concerning the very deities to whom he had been entrusted: “In Agni, Indra, Āditya, and the Viśve Devas, has your studenthood been fulfilled?”

When he has replied, “It has been fulfilled, sir,” while [the student] stands west of the fire facing east, the preceptor, wrapping an unblemished cloth three times clockwise around his head, having placed the fringes on the top so that it will not slip down,

[says:] “For three nights, putting fuel on the fire, begging food, sleeping on the ground, and serving the guru, restrained in speech, heedful, fasting in the forest, in a temple, or at the Agnihotra, dwell.”

Here indeed some observe those very rules standing; they sit down only at night.

The student, eating no meat, going out of the village, must not look at these: reasons for suspension of recitation, one who touches a corpse, raw flesh, a Caṇḍāla, a woman who has newly given birth, a woman with clipped fingers, a cremation ground, and all dark-colored things that could not enter the mouth.

In the northeast direction, in a pure place, when the sun has risen, he recites [the texts] according to the rule of recitation to him who is restrained in speech and wearing a turban.

This rule applies only to the Mahānāmnī verses.

Then in the subsequent sections, he should perform daily Vedic recitation in this way: the other listens to the preceptor.

He gives to the preceptor a turban, a vessel of clarified butter, and a sacrificial fee, with: “Thee, that…”

and with: “High in heaven…”

Or everything with the praṇava [oṃ].

Here indeed some prepare a boiled mess of rice for the Viśve Devas in all sections.

“According to how he was entrusted,” says Māṇḍūkeya.