Swearing or oath is known as sapatha or shapath in Hinduism. It is also a vow to complete an action or achieve an undertaking. It is done by taking an oath or swearing on the name of someone or something. It is required to be taken in the name of truth by a Brahmin, in the name of vehicles and weapons by a kshatriya, and in the name of cows, seeds and gold by a vaishya. Others swear by the name of ill fate they may bring upon themselves in case of false declarations. Some others may be asked to hold a stick of fire placed on a leaf of the fig tree or enter water or touch the head of his son or daughter, while making an oath.
Swearing can be done by holding the beads of holy basil (tulsi) or the water of Ganga in the hand, or in front of an idol of God, or by touching a Brahmin, a cow or fire. Instances of kings swearing in the name of their dear ones or ideals to complete a venture (like vanquishing a foe) or to offer their heads to the ishta devatas (favorite deities) in case of failure are not unknown.
In the Ramayana, Bharata swore not to return to Ayodhya without Rama and declared his intention to enter the fire at the end of the fourteenth year if Rama failed to come back the day his exile ended. The instance of samshaptaka (swearing) not to return without killing Arjuna on the thirteenth day, taken by the king of Trigarta in the Mahabharata is also well known.
Jnana Vapi well in Kashi Vishwanath Temple is a place where the kings, leaders and soldiers swore to offer their heads either as fulfillment of their vow or non-fulfillment, according to local tradition. It is strongly believed that a person who makes false vows or does not fulfill a vow will be hurled into the hell known as the glowing volcano (jwalamukhi) after death. Hence one is warned against making a false oath.
The two epics, the Ramayana and the Mahabharata, are full of incidents of vows being taken and fulfilled. In the Ramayana, we see that king Bhagiratha took a vow to bring the Ganga from the celestial region and emerged successful. King Vishwamitra took a vow to become a brahmarishi. After years of penance and passing through much travail, he became a brahmarishi. In the Ramayana, Rama takes a vow to kill Ravana and, with the help of Sugriva, achieves his aim. An old woman, Sabari, takes a vow to wait for Rama in a remote ashrama in the forest. After worshipping Rama, she fulfills her vow and goes to the other world. Bharata’s vow seems to be the greatest; he took a vow not to enter Ayodhya and not to wear royal clothes till Rama returned to the capital. After fourteen years, his vow was realized.