Mahabharata Anushasna Parva Chapter 125:6

Mahabharata Anushasna Parva (Dana Dharma Parva) Chapter 125:6 Those men who, endued with faith, beget offspring, rescue their deceased ancestors from miserable Hell'. Hearing these words of the Pitris, Vriddha-Gargya, possessed of wealth of penances and high energy, became filled with wonder so that the hair on his body stood erect. Addressing them he said, 'Ye that are all possessed of wealth of penances, tell us what the merits are that attach to the setting free of bulls endued with blue complexion. What merits, again, attach to the gift of lamps in the season of rains and the gift of water with sesame seeds?' The Pitris said, 'If a bull of blue complexion, upon being set free, raises a (small) quantity of water with its tail, the Pitris (of the person that has set that bull free) become gratified with that water for full sixty thousand years. The mud such a bull raises with its horns from the banks (of a river or lake), succeeds, without doubt, in sending the Pitris (of the person that sets the animal free) to the region of Soma. By giving lamps in the season of rains, one shines with effulgence like Soma himself. The man who gives lamps is never subject to the attribute of Darkness. Those men who make gifts, on the day of the new moon, of sesame seeds and water, mixed with honey and using a vessel of copper, O thou that art possessed of wealth of penances, are regarded as duly performing a Sraddha with all its mysteries. These men get children of sound health and cheerful minds. The merit acquired by the giver of the Pinda (to the Pitris) takes the form of the growth of his race. Verily, he who performs these acts with faith, becomes freed from the debt he owes to the Pitris. Even thus has been laid down the proper time for the performance of the Sraddha, the ordinance in respect of the rites to be observed, the proper person that should be fed at the Sraddha, and the merits that attach to it.' I have declared everything to thee in due order.