Udyoga Parva 180
1 “‘Bhishma said, “O lord, repeatedly urged by that maiden to slay Bhishma, Rama replied unto that weeping girl, saying, ‘O daughter of Kasi, O thou of the fairest complexion, I do not, on any account, take up arms now except for the sake of those that are conversant with the Vedas. Tell me, therefore, what else I can do for thee? Both Bhishma and Salwa are, O princess, exceedingly obedient to me. Do not grieve, I will accomplish thy object. I will not, however, O beautiful lady, take up arms, except at the command of Brahmanas. This hath been my rule of conduct.’
2 “‘“Amva said, ‘My misery, O holy one, should by any means be dispelled by thee. That misery of mine hath been caused by Bhishma. Slay him, therefore, O lord, without much delay.’
3 “‘“Rama said, ‘O daughter of Kasi, say but the word and Bhishma, however, deserving of reverence from thee, will, at my word, take up thy feet on his head!’
4 “‘“Amva said, ‘O Rama, slay in battle that Bhishma who roareth like an Asura. Indeed, summoned to the encounter (by him), slay him, O Rama, if thou wishest (to do) what is agreeable to me. It behoveth thee, besides, to make thy promise true.’”
5 “‘Bhishma continued, “While, O king, Rama and Amva were talking thus with each other, the Rishi (Akritavrana) of highly virtuous soul said these words, ‘It behoveth thee not, O mighty-armed one, to desert this girl that seeketh thy protection! If summoned to battle, Bhishma cometh to the encounter and sayeth--“I am vanquished,” or, if he obeyeth thy words, then that which this maiden seeketh will be accomplished, O son of Bhrigu’s race, and the words spoken by thee, O hero, will also, O lord, be true! This also was, O great Muni, the vow then made by thee, O Rama,--the vow made by thee before Brahmanas after thou hadst conquered all the Kshatriyas, viz., that thou wouldst slay in battle the person, be he a Brahmana, a Kshatriya, a Vaisya, or a Sudra, who would be a foe to the Brahmanas. Thou hadst further promised that as long as thou wouldst live thou wouldst not abandon those that would come to thee in fright and seek thy protection, and that thou wouldst, O Bhargava, slay that proud warrior who would vanquish in battle all the assembled Kshatriyas of the earth! O Rama, even Bhishma, that perpetuator of Kuru’s race, hath achieved such success (over all the Kshatriyas)! Approaching him, O son of Bhrigu’s race, encounter him now in battle!’
6 “‘“Rama said, ‘O best of Rishis, I recollect that vow of mine made before. I will, however (in the present instance) do that which conciliation may point out. That task which the daughter of Kasi hath in her mind is a grave one, O Brahmana! Taking this maiden with me, I will repair myself to the place where Bhishma is. If Bhishma, proud of his achievements in battle, do not obey my behest, I will then slay that arrogant wight. Even this is my fixed resolve. The arrows shot by me do not stick to the bodies of embodied creatures (but pass them through). This is known to you from what you saw in my encounters with the Kshatriyas!’ Having said this, Rama then, along with all those seekers of Brahma, resolved to depart from that asylum, and the great ascetic then rose from his seat. Then all those ascetics passing that night there, performed (on the next morning) their homa-rites and recited their prayers. And then they all set out, desirous of taking my life. And Rama, accompanied by all those devotees of Brahma, then came to Kurukshetra, O monarch, with that maiden, O Bharata, in their company. And those high-souled ascetics, with that foremost one of Bhrigu’s race at head, having arrived on the banks of the stream of Saraswati, quartered themselves there.”’”