The Most Ancient Lives of Saint Patrick/The Life and Acts of St. Patrick/Chapter 158
Fire is also seen to issue from his Mouth.
And he preached the word of God unto a certain great man, to whom it seemed that fire issuing from the mouth of the saint entered into his ears and mouth, and filled him internally with its heat. And this fire was not consuming, but illumining; not burning, but shining; as he who so experienced related unto the saint, saying, "I behold a flaming fire to issue from thy mouth, and penetrate my body and my inmost heart." Then to him the saint: "Our God is the true light illumining every man at his entrance into the world; our God, who came to send upon earth that fire which He desireth should burn in the hearts of the faithful: for the word of the Lord is bright, and his speech is as fire; whereof by my preaching hast thou had in thyself the proof."