Viṣṇu Purāṇa | Book 3 - Chapter 14
"Let the devout performer of an ancestral oblation propitiate Brahmā, Indra, Rudra, the Aśvīns, the sun, fire, the Vāsus, the winds, the Viśvadevas, the sages, birds, men, animals, reptiles, progenitors, and all existent things,
by offering adoration to them monthly, on the fifteenth day of the moon's wane (or dark fortnight), or on the eighth day of the same period in certain months, or at particular seasons, as I will explain.
"When a householder finds that any circumstance has occurred, or a distinguished guest has arrived, on which account ancestral ceremonies are appropriate, he should celebrate them.
He should offer a voluntary sacrifice upon any atmospheric portent, at the equinoctial and solstice periods, at eclipses of the sun and moon, on the sun's entrance into a zodiacal sign, upon unpropitious aspects of the planets and asterisms, on dreaming unlucky dreams, and on eating the grain of the year's harvest.
The Pitris derive satisfaction for eight years from ancestral offerings upon the day of new moon when the star of the conjunction is Anurādhā, Viśākhā, or Svātī; and for twelve years when it is Puṣyā, Ardrā, or Punarvasu.
It is not easy for a man to accomplish the task for those who are desirous of worshipping the Pitris or the gods on a day of new moon when the stars are those of Dhaniṣṭhā, Purvabhādrapadā, or Śatābhiṣā.
Hear also an account of another class of Śrāddhas, which afford especial contentment to progenitors, as explained by Sanatkumāra, the son of Brahmā, to the magnanimous Purūravas, when full of faith and devotion to the Pitris he inquired how he might please them:
The third lunar day of the month Vaiśākh (April, May), and the ninth of Kārtika (October, November), in the light fortnight; the thirteenth of Nabha (July, August), and the fifteenth of Māgha (January, February), in the dark fortnight are called by ancient teachers the anniversaries of the first day of a Yuga, or age (Yugādya), and are esteemed most sacred:
On these days, water mixed with sesame-seeds should be regularly presented to the progenitors of mankind; as well as on every solar and lunar eclipse;
on the eighth lunation of the dark fortnights of Agrahāyaṇa, Māgha, and Phālguna (December--February); on the two days commencing the solstices, when the nights and days alternately begin to diminish;
on those days which are the anniversaries of the beginning of the Manvantaras; when the sun is in the path of the goat; and on all occurrences of meteoric phenomena.
A Śrāddha at these seasons makes Pitris happy for a thousand years: such is the secret which they have imparted.
The fifteenth day of the dark half of the month Māgha, when united with the conjunction of the asterism over which Varuṇa presides (Satābhiṣā), is a season of no little sanctity, when offerings are especially grateful to the progenitors.
Food and water presented by men who are of respectable families, when the asterism Dhaniṣṭhā is combined with the day of new moon, content the Pitris for ten thousand years; whilst they repose for a whole age when satisfied by offerings made on the day of new moon when Ārdrā is the lunar mansion.
"He who, after having offered food and libations to the Pitris, bathes in the Ganges, Satlaj, Vipāśā (Beyah), Sarasvatī, or the Gomatī at Naimiṣa, expiates all his sins.
The Pitris also say:
'After having received satisfaction for a twelvemonth, we shall further derive gratification by libations offered by our descendants at some place of pilgrimage, at the end of the dark fortnight of Māgha.'
The songs of the Pitris confer purity of heart, integrity of wealth, prosperous seasons, perfect rites, and devout faith; all that men can desire.
Hear the verses that constitute those songs, by listening to which all those advantages will be secured, oh prince, by you:
'That enlightened individual who begrudges not his wealth, but presents us with cakes, shall be born in a distinguished family.
Prosperous and affluent shall that man ever be, who in honour of us gives to the Brahmans, if he is wealthy, jewels, clothes, land, conveyances, wealth, or any valuable presents; or who, with faith and humility, entertains them with food, according to his means, at proper times.
If he cannot afford to give them dressed food, he must, in proportion to his ability, present them with unboiled grain, or such gifts, however trifling, as he can bestow.
Should he be utterly unable even to do this, he must give to some eminent Brahman, bowing at the same time before him, sesame-seeds adhering to the tips of his fingers, and sprinkle water to us, from the palms of his hands, upon the ground;
or he must gather, as he may, fodder for a day, and give it to a cow; by which he will, if firm in faith, yield us satisfaction.
If nothing of this kind is practicable, he must go to a forest, and lift up his arms to the sun and other regents of the spheres, and say aloud--I have no money, nor property, nor grain, nor anything whatever for an ancestral offering. Bowing therefore to my ancestors, I hope the progenitors will be satisfied with these arms tossed up in the air in devotion.'
These are the words of the Pitris themselves; and he who endeavours, with such means as he may possess, to fulfil their wishes, performs the ancestral rite called Śrāddha."