This is a preparatory oil sketch for one of the eight frescoes, now lost, by Bayeu for the dome of the collegiate church at La Granja de San Ildefonso, Segovia. They depicted the exaltation of the Trinity and the revelation of the existence of God. A seraphim with a live coal taken from the temple altar approaches Isaiah, kneeling before a vision of God, and touches him with it in order to leave him free of sin (Isaiah 6, 1-8).