The same story about the Desert Fathers, told two ways. Why not fire?
Lot went to Joseph and said, ‘Abba, as far as I can, I keep a moderate rule, with a little fasting, and prayer, and meditation, and quiet: and as far as I can I try to cleanse my heart of evil thoughts. What else should I do?’ Then the hermit stood up and spread out his hands to heaven, and his fingers shone like ten flames of fire, and he said, ‘If you will, you can become all flame.’
The Desert Fathers: Sayings of the Early Christian Monks by Benedicta Ward
Abbot Lot came to Abbot Joseph and said: Father, according as I am able, I keep my little rule, and my little fast, my prayer, meditation and contemplative silence; and according as I am able I strive to cleanse my heart of thoughts: now what more should I do? The elder rose up in reply and stretched out his hands to heaven, and his fingers became like ten lamps of fire. He said: Why not be totally changed into fire?
The Wisdom of the Desert by Thomas Merton