On The Memorable Moment

The explanation for three knots are available in the Internet are many. There may be variations in the number of knots by the bridegroom and the sister in law. The bridegroom ties the first knot and two more knots by the sister in law..

(i) Three Knots are trinities:

The three knots symbolizes Brahma, Vishnu and Rudhra. It means the Brahma, Vishnu and Rudhra are the Husband for the bride.

(ii) In laws are God:

Three knots symbolize three different aspects of a married woman - the first knot represents her obedience to her husband, the second to his parents and the third represents her respect for God.

“May our prayers and worship be alike, and may our devotional offerings be one and the same.” Rig Veda Samhita 10.191.3

(iii) Three knots are three purusarthas:

Dharma, Artha:and Kama (the first three purusarthas) have become common in this life for the couple.

(iv)Three knots are the three custodians:

(Manu Smiiti 9.3)

“Father protects (her) in childhood, husband protects (her) in youth, and sons protect (her) in old age. A woman cannot be left unprotected.”

(v) Three knots are husband, wife and children:

.“Unite, O Lord, this couple like a pair of lovebirds. May they be surrounded by children living both long and happy ” Atharva Veda Samhita 14.2.64

(vi) Three knots are three terrestrial husbands:

According to the Sruti texts, every woman is wedded first to Soma, then Gandharva and then Agni before marrying her earthly partner.

Vedic Vivaha Mantra:
Bridegroom tells these mantras to bride.

RigVeda 10.85.40:
Somah prathamah vivide gandharvo vivida uttarah.
Tritiyo agnishte patisturiaste manushyajah.

Soma recieved first- 'somah prathamah vivide', Gandharva recieved afterwards- 'gandharvah uttarah vivide'. Agni is your third husband- 'Agnih te tritiyah patih', son of man is your fourth- 'manushyajah te turyah.

Soma obtained her first of all; next the Gandharva was her lord.
Agai was thy third husband: now one born of woman is thy fourth.

Three knots are the three terrestrial husbands and the Mangalasutra becomes the earthly husband.

Meaning:
Soma gives strength, Gandharva gives beauty and the Agni gives yavvana for the bride.