By St. John Moschos
One of the fathers said that there was one of the elders who was pure and holy; who, when he was celebrating the Eucharist, use to see angels standing to his right hand and to his left. He had learned the eucharistic service from heretics but, as he was unlearned in theological matters, when he made the offering he spoke the prayer in all simplicity and innocense, unaware that he was at fault.
By the Providence of God, there came to him a brother who was skilled in theology and it happened that the elder offered the Eucharist in his presence. The brother (who was a deacon) said to him: "Father, these things which you say at the Eucharist are not in accordance with the Orthodox faith; they are heresy." Since the elder could see angels when he was celebrating, he paid no attention to what was said, and thought nothing of it. But the deacon went on saying: "You are at fault, good elder; the Church does not allow those things to be said."
When the elder realized that he was being accused and blamed by the deacon, the next time he saw the angels, he asked them: "When the deacon speaks to me like this, what am I to make of it?" They said to him: "Pay attention to him; he is giving good counsel." The elder said to them: "Then why did you not tell me so?" They said: "Because God has ordained that men should be corrected by men", and from that time forth he accepted correction, giving thanks to God and to the brother.
From The Spiritual Meadow, 199.