Mbh 7.17.2b

And equipped in mail, bathed in clarified butter, clad in robes of Kusa grass, and with their bow-strings serving as girdles, those heroes, who had given away hundreds and thousands as presents to Brahmanas, who had performed many sacrifices, had been blessed with children, and were deserving of blessed regions hereafter, who had nothing more to do in this world, who were deserving of blessed regions hereafter, who were prepared to lay down their lives in battle, and who devoted their souls to the attainment of fame and victory, who were desirous of soon repairing by fair fight to those regions (hereafter) that are attainable by means only of sacrifices, with abundant presents to Brahmanas, and by means also of the rites, the chief amongst which are Brahmacharya and study of the Vedas, those heroes, having each gratified Brahmanas by giving them gold,[30] and kine, and robes, and having addressed one another in loving discourse, ignited those fires and took that vow in battle. And in the presence of those fires, firmly resolved, they took that vow.