On the day of Avani Avittam, the sacred thread worn is changed and it is usually a community observance and takes place on the banks of a pond or river. Avani is the name of the Tamil month and Avittam is one of the 27 nakshatras or stars. On this day, a Mahasankalpam or a vow is taken for atonement of all our sins in the past year. The Brahmins take a holy dip and wear a new holy thread called Yajnopavit or Janeyu.
The first step is a ‘prayashchita’ A prayer to atone the sins. It says, “For the removal of all my sins and thereby to secure a divine blessing and for qualifing myself to perform the essential duties of Brahmanas as prescribed in the vedas and smritis and adopted by the really good in their conduct I put on this Yagnopavita”.
When the thread is worn another mantra is recited which means -”I put on the sacred thread which is highly pure, is inseparable from God, is capable of prolonging life and is the foremost in the accomplishment of a Brahmana. May such pure Yagnopavita bring strength and dignity.
While removing the old thread, the mantra means -”I throw away the broken dirty old thread, may the new one bring on long life and Brahmana’s brilliance.
Avani Avittam Significance
Upakramam means the beginning. On this day the Yajurvedis begin to read Yajur Veda for next six months. The day is auspicious because as per Indian mythology Lord Vishnu was incarnated as Lord Hayagriva,the lord of knowledge, the one who restored the Vedas to Brahma.
How it is celebrated
On this day, Brahmin boys are bestowed with the Sacred Thread (Yajnopavit or Janeyu). It is said that the third eye, that is the eye of wisdom opens on this day. A Mahasankalpam or a vow is taken for the expiation of all the sins in the past year. Thereafter Brahmins take a holy water dip and wear a new holy thread called Yajnopavit or Janeyu.
Procedure followed on the day
First the Rishi Tharpanam (offering prayers to the ancient Rishis) is read out. Brahmin bachelors perform ‘Samitha Daanam’ and ‘kamo karshith japam’ after Mahasankalpam. Thereafter, Kaanda Rishi tharpanam is performed with the help of family priest or elders. As per the rituals, all the male members should have a light meal at night.
Next day after an early bath, ‘Gayathri Japam’ is read out by everyone. Gayatri Japam Sankalmpam is noted for the chanting of the Gayatri Mantra for 1008 or 108 times. Sama Vedi Brahmins perform the ritual the day after Shravan Amavasi.
This day is also auspicious as the Brahmins offer libations of water to their ancestors to whom they owe their birth and to the great Rishis to whom they are highly indebted for spiritual knowledge and the Vedas themselves.
Source Hindu blog.