What ceremony fulfils the religious part of a Hindu wedding?
Taking the pheras simply means going around the fire. Amongst Hindus it is customary for the couple getting married to go around the fire seven times in a slow formal walk. Sikhs walk around the Guru Granth Sahib. According to the religious texts, it is customary to circumambulate the fire four times. However, many priests now have it done seven times, confusing this with saptpadi, which is a separate rite. This ceremony fulfils religious aspects of the marriage and is symbolic of the irrevocable faith a couple must have in each other.
During the ceremony the couple walk around the fire slowly amidst chants of wedding mantras. The two promise that in the presence of Agnidev (the god of fire), parents, relatives and friends they are getting religiously bound in a mutual relationship. They assert that they are morally bound and shall fulfill their promise to the best of their abilities. This ceremony is performed before the fire since it symbolizes energy or Surya, the sun. Surya is the soul of the living world and a form of Vishnu. Therefore, when one walks around the fire, it is symbolic of going around with God as witness. Fire has the potential of destroying one's sins through burning. Therefore, marriage is conducted before the fire.
The couple walks clockwise. In the first four rounds, the bride leads and the groom follows. In the final three, the groom leads and the bride follows. The priest reads mantras during each round. At the end of each round the couple halt, repeat the Gayatri mantra, and offer prayers to the fire. During this ceremony the bride leads four times and the groom thrice. It indicates that in all household matters she shall lead, since she is more experienced in this sphere. In professional or vocational fields, the man shall lead because he is more experienced. When both consult each other in matters pertaining to the home and outside and work in unison, they establish a successful family together.