It is scarcely surprising that the Cid was not trusted by Alfonso of Leon, when he, in his turn, succeeded to the crown of Castile. But for the moment Alfonso was not only deprived of his throne and of his liberty by his more successful brother, but he was compelled to purchase his life by a promise to enter the monastery of Sahagun. Disregarding this vow, and making good his escape to Toledo, the royal refugee was received with the usual hospitality of the Arab by El Mamun, the Moslem ruler of the city, who sheltered and entertained him, as he himself admitted, “like a son.” Sancho meanwhile had turned his arms against his brother Garcia, whom he dispossessed of his territories; against his sister Elvira, who met with a similar fate, and, lastly, against his sister Urraca, who withstood him boldly in her city of Zamora. And not only did this time-honored fortress resist the attack of Sancho and his wily major-general, but the king was slain outside the walls of the city by one of his sister’s knights. Alfonso thus not only recovered his own kingdom of Leon, but, swearing perpetual friendship with El Mamun of Toledo, he was elected king of Castile by the Commons assembled at Burgos; and the defeated refugee of 1071 found himself, in less than two years, the greatest prince in Christian Spain; Alfonso the Sixth of Leon and of Castile. Yet the legend runs that Alfonso was compelled to undergo the indignity of a public examination, and a triple oath before the knights and nobles assembled at Burgos, to the effect that he had had no share in the murder of King Sancho; and the oath was administered by Ruy Diaz of Bivar, the companion in arms of the Castilian king, sometime the faithless enemy of Carrion, but now the acknowledged leader of the Castilian nobility. Alfonso of Leon may have forgiven the treachery in the field, but he never forgot the insult in the Council. He restrained his indignation, however, and was even induced by reasons of State to grant to the bold Castilian lord the hand of his cousin Ximena in marriage, and to intrust him with the command of an expedition into Andalusia. But the royal favor was of brief duration; and in 1081 we find that Roderic, partly owing to the intrigues of Garcia Ordonez, and partly to the enduring enmity of the king, was banished from the Christian dominions.