"Entering a newly-built house for the first time", this is a very important occasion for any family, since acquiring property is no easy task. It is believed that the new acquisition is susceptible to evil forces and jealousy and therefore various "safeguard" ceremonies must be performed. Vastu pratishtha, or the construction and occupation of a house, was an important ceremony even during the Vedic period. Gods and planets were and still are symbolically invited to the construction site to enable the work to progress smoothly. After construction is completed, another puja is performed to appease the gods so that they bless the house and its occupants. These ceremonies are also thanksgivings to the gods and the ancestors for the boon of a house.
When the house is ready to be occupied, a muhurta is selected for grihya pravesha puja, which consists mainly of Ganesha puja, invoking the deities and one`s ancestors, and the havan. On the day of the ceremony, the newly-constructed house is cleaned and decorated. A garland of mango leaves is hung across the main doorway as a protective barrier against evil. Sometimes, poles are erected outside the house around which banana leaves, symbols of plenty, are wound and tied, forming a festive archway at the threshold. Both the mango and the banana tree are considered auspicious, since they are symbols of fertility and prosperity.
Before entering the house, a ceremony called Vastushanti is performed. This ceremony aims to appease the gods and planets so that the owner of the house is blessed with good fortune. Like any other puja, this also begins with Ganesha puja, to remove all obstacles. After that, a mandala is drawn to invoke the gods and nine planets, who act as witnesses to the ceremony. The next ritual is the oblation to the havan. Camphor, sesame, grain and fuel sticks, along with other ingredients, are offered to the fire, which is supposed to convey them to the gods. The family must carry the havan kunda into every room. The various medicinal ingredients in the smoke from the havan disinfect and purify the air within.
The house is now encircled thrice with thread, starting from the east which is considered the most auspicious direction. At the same time, water is poured in a continuous stream around the house. Both these signify the erection of protective barriers around the house to keep away evil influences, and are done to the accompaniment of the Rakshoghna Mantra and the Pavamana Mantra.
Next, a pit is dug in the south-east corner of the boundary of the house. The sides of the pit are fortified with cowdung paste and the pit is worshipped. A brick box containing corn, moss, and flowers is lowered into the pit, which is then filled up. Since corn symbolises fertility, this is believed to ensure prosperity and fertility in and around the house.
Finally, the owner-family and the Brahmins specially invited for the occasion, enter the house. The head of the family holds a jar of water in his hands, with durva placed on top. The jar is placed on a heap of corn to the recitation of mantras. Holy water is sprinkled around the house to frighten away evil spirits. With this, grihya pravesha is completed. The Brahmins and other guests are fed.
The Grihyasutras give detailed instructions about the kind of land that should be chosen for constructing a house or temple, the direction it should face and the ceremonies to be performed at each stage. The Matsya Purana elaborates which stages during construction are important, like laying the foundation, and raising the first door, and explains that grihya pravesha puja should be performed at these stages.
This ceremony is still performed in the traditional manner. After Ganesha puja, the deities and ancestors are invoked, and finally the havan is performed. One of many rituals which symbolise the erection of protective barriers around the house is performed, and then the invited guests are fed.