This fast is observed on the full moon day of Margashirsha month. Lord Narayan is worshiped on this day. On this day, the Moon completely influences the Earth and the water element. This day is considered as the day of divinity. The full moon of Margashirsha month is doubly auspicious, so meditation, charity and bathing are especially beneficial.
There is a law to worship Lord Narayan in the fast of Margashirsha Purnima. First of all take a holy bath. Wear white clothes first and more, after that chant the mantra 'Om Namo Narayan' in the fast. Set up a fire at the Chakor altar to perform Havan. Offer oil, ghee, boora, etc. After the end of the havan, one should worship God and offer his fast to him and say the following verses-
paurn maasyan niraahaarah dev tavaagyya |
mokshyaadi pundarika mokshahvi sharanan bhav ||
Oh god Pundarikaksha! I will take food on the next day by keeping a fast on the full moon with your permission. You take me under your shelter.
In this way, after dedicating the fast to the Lord, on the rise of the moon in the evening, sit on both knees and offer Arghya to the moon with white flowers, akshat, sandalwood, water. While offering arghya, pray to the moon.
Oh god! You have been born in the Atri clan and you have appeared in Ksheer Sagar. Please accept my request. After offering Arghya to the moon, pray with folded hands.
Hey, God! The tops are adorned with white rays, I salute you, you are the king of the dwijas. I salute you. You are Rohini's husband, I salute you.
In this way, at night, sleep near the idol of God. On the next day, feed Brahmins in the morning and send them off by donating.