From Catechism: Lessons on the Sacraments and Ten Commandments by Saint Alphonsus Ligouri.
To understand the great efficacy of this sacrament in imparting spiritual strength to the faithful, it is enough to know the facts related by St. Gregory Nazianzen and Prudentius. Julian the Apostate wished one day to offer sacrifice to his false gods, and had everything prepared; but, at the moment they wished to offer the sacrifice, the knives refused to cut, the fire was instantly extinguished, and the ministers became immovable as a rock. The sacrificing priest said, There must be some one present who has been baptized or confirmed. The emperor asked if there were in the assembly any person who had been baptized or confirmed. Behold! a boy, who had received confirmation a little before, came forward, and said, "Yes, sir, I have been confirmed; and therefore I have besought my God to prevent the impiety of the sacrifice, and He has heard my prayer." Julian was struck with astonishment, and covered with confusion, by the prodigy; he gave up the sacrifice, and withdrew from the temple.