The Secret of the Treason
XI. But when the Counts of Castille saw how Rodrigo increased day by day in honour, they took counsel together that they should plot with the Moors, and fix a day of battle with them on the day of the Holy Cross in May, and that they should invite Rodrigo to this battle, and contrive with the Moors that they should slay him; by which means they should be revenged upon him, and remain masters of Castille, which now because of him they could not be.
This counsel they sent to communicate to the Moors and to the Moorish Kings who were Rodrigo's vassals, being those whom he had made prisoners and set at liberty. But they, when they saw this counsel and the falsehood which was devised, took the letters of the Counts, and sent them to Rodrigo their Lord, and sent to tell him all the secret of the treason. And Rodrigo thanked them greatly for their good faith...
(Text from Chronicle of The Cid, translated from the Spanish by Richard Southey, 1883. Image made in Fyre.)