Abba Lot came to visit Abba Joseph and said: "Abba, when I am able, I recite a short office, I fast a little, I pray, I meditate, I stay recollected. As far as I can I try to keep my thought pure. What else should I do?"
Then Abba Joseph got up. He stretched out his hands to heaven and his fingers became like burning lamps.
He said to Abba Lot: "If you will, become all fire."
Come to think of it, the epiphany of the burning bush which Moses witnessed is a perfect image of grace at work: just as the bush was burning but not consumed, so too does grace transform and transfigure our nature.
And this is certain, since obedience is a holocaust in which the whole man without the slightest reserve is offered in the fire of charity to his Creator and Lord through the hands of His ministers.
-St. Ignatius Loyola, Letter "On Perfect Obedience" Rome, March 26, 1553