Pind Sammelan or Spindi is a ritual performed in Hinduism on the 13th day of death of somebody. This ritual is performed to place the departed soul with the ancestors and God. It is believed that before the ritual the departed soul is a preta (evil spirit), and after performing this ritual, the soul will become "pitr" (good spirit) and will be included in the ancestors.
In North India, this ritual is called the terahvin.[1][2][3]
... Ashes of the dead are immersed in a river, preferrably [sic] Ganga. The thirteenth day or final day of mourning is known as terahvin. It can be held any day after the ashes are immersed though generally is observed no later than the thirteenth day. It is a way of bidding goodbye to the soul. Daan, that is, gift of a new bed, shoes, clothes, quilt, ...
... Other Hindus, they pray from the Gita or other slokas. And on the 13th day from death, Sikhs who have turbans, they necessarily have Guru Granth Sahib path. For 13 days they go on reading, and on the last day it is completed and special functions are held ...
... On terahvin, five pandits are called to perform purificatory puja and havan. Brahmans are treated to fried food, sweets and also given cash and presentations like a string-cot, bed, a stick, juti (shoes) and four or five utensils by way ...