The last day of the fortnight which is sacred for offering oblations to departed ancestors, the new moon day, is considered as the most important day in the year for performing ceremonies and rites.This dark fortnight during the period September-October is known as the Mahalaya Paksha.The day of Mahalaya Amavasya is the day of great significance and importance to all Hindus.It is the annual festival for propitiating the spirits of ancestors, with prayers for peace. The fortnight preceding the new moon is specially consecrated for the propitiation of such departed spirits. The ceremonies performed in honour of ancestors during each day of this fortnight are considered to be equal to those performed at Gaya. The principle in all such rites is the worship of the departed souls and the satisfaction of their wishes so that they might be in peace during the rest of the year.
According to ancient Hindu texts, on Mahalaya Amavasya, there is a conjunction of the sun and the moon and that the sun enters the sign Virgo (Kanya). On this day, it is believed that ancestors leave their abode and come down to the world of mortals and occupy the houses of their descendants. Hindus offer oblation of water to the departed on every new-moon day. The prescribed rites are also performed every year on the death anniversary.This is the Sraddha ceremony. The special importance of these observances particularly during Mahalaya is that such ceremonies done during this fortnight have a very special effect. The offerings reach the departed souls immediately and directly, due to a boon from Lord Yama.Karna, a renowned hero according to the Mahabharata was a very generous man. After his death the great charity he had done on earth was returned to him hundred fold in heaven. However all he got was gold and silver.There was no food as he been very generous only with gold and silver during his life. He prayed to God of Death and was sent back to earth for fourteen days to make up for this.
During the fourteen days he fed the poor and offered oblations of water. On his return to the heaven he was offered food in plenty. The fourteen days are commemorated in the Mahalaya Paksha. It is believed that due to the grace of Lord Yama, it came to be so ordained that such rites done at this particular period acquired unique merits. Even those who died without progeny received these oblations given on this Pitri-paksha Amavasya day. All those who had failed to do deeds of charity and Anna-Dana (gift of food) and were thus denied these comforts in the Pitri Loka, benefited by these ceremonies.
Those deceased whose date of death is not known and whose annual Sraddha cannot be done, they also get these oblations of Pitri Paksha. Souls whose life was cut off by violent accidental or unnatural death and to whom, therefore, offerings cannot reach in the ordinary course, to them, too, the Ptripaksha offerings reach directly. Hindus now observe this Paksha with great faith and worship and charity in the form of food is considered important during this period.