King Shantanu had a son through Ganga. When Ganga handed him over to Shantanu’s care, she told Shantanu that Devavrata had been trained by Sukracharya, Parasurama and Brihaspati and would be an even greater warrior than Shantanu himself. Devavrata, however, was to prove his greatness in other ways as well, elaborated Rama Dikshitar in a discourse.
One day, Shantanu was out hunting when he saw a beautiful woman called Satyavathi and fell in love with her. But her family insisted that Shantanu would have to make the sons born to Satyavathi the heirs to the throne. But how could Shantanu do that, when he already had a grown up son, Devavrata? So Shantanu went back without marrying Satyavathi.
When Devavrata came to know what had happened, he promised Satyavathi that he would never ascend the throne. But her family wanted to know what would happen if Devavrata were to marry and beget children. Devavrata then promised that he would never marry or seek the company of women. When he made this promise, the celestials shook with fear and he came to be known as Bhishma, because of his terrible oath. When Shantanu came to know of his son’s oath, he gave him a boon. Bhishma could die at will. That was why during the Kurukshetra war, Bhishma lay on a bed of arrows, waiting for the right time to depart. He never once wavered from his oath, not even when Satyavathi, upon the death of her sons, asked him to marry to keep the lineage alive. Bhishma knew the sanctity of a promise.
When Yudishtra was agitated after the war, unhappy about all the destruction, Krishna told him to seek the advice of Bhishma.
