What those who were to be initiated promised on entering the Church, of the witnesses to these promises, and wherefore they then turned themselves to the East.
5. After this the Holy of holies was opened to you, you entered the sanctuary of regeneration; recall what you were asked, and remember what you answered. You renounced the devil and his works, the world with its luxury and pleasures. That utterance of yours is preserved not in the tombs of the dead, but in the book of the living.
6. You saw there the deacon, you saw the priest, you saw the chief priest [i.e. the bishop]. Consider not the bodily forms, but the grace of the Mysteries. You spoke in the presence of the angels, as it is written: “For the priest's lips keep knowledge, and they seek the law at his mouth, for he is the angel of the Lord Almighty.” There is no place for deception nor for denial. He is an angel who proclaims the kingdom of Christ and eternal life. He is to be esteemed by you not according to his appearance, but according to his office. Consider what he delivered, reflect upon the rule of life he gave you, recognize his position.
7. You entered, then, that you might discern your adversary, whom you were to renounce as it were to his face, then you turned to the east; for he who renounces the devil turns to Christ, and beholds Him face to face.
Source: On the Mysteries (New Advent)