Abba Gregorius, the former Imperial guard, told us that there was a brother in the coenobium of Choziba, who was learning the ritual of oblation of the Holy Sacrifice. Now, one day he was sent to bring the loaves of bread for the offering, and while he was on his way back to the monastery, he recited the ritual of oblation, as if chanting hymns. Then the deacons put those same offerings in the offering plate on the holy altar. But, when those oblations were offered by Abba John, surnamed the Chozebite - then the priest (of the monastery), later to become bishop of Caesarea of Palestine - he did not see the advent of the Holy Spirit, as he always did. John was distressed, lest he himself had sinned and for that reason the Holy Spirit had not come; and so he went into the diaconicon, shedding tears and throwing himself on his face. But God’s messenger appeared to him and said: “Since the brother who brought the offering bread has recited the holy oblation on the road, these offerings have been already consecrated and are now perfect”. And from that time on the Elder established the rule that nobody who had not been ordained should learn the ritual of the Holy Sacrifice, not should anybody recite it casually at any time, but only in hallowed place.
(transl. Leah Di Segni)