Augustine contends that God appeared to man in the Old Testament through the intermediate ministry of angels. After Adam and Eve are kicked out of the garden/sanctuary of Eden, an angel is placed at its gates to keep men out of the meeting place of God and man. Golden angels also guarded the Holy of Holies in the Temple.
So in the Old Testament, if man wanted to meet with God, he had to go through the angels.
But now, in the New Testament, God comes as man. Now man sits in the seat of authority. Man has the keys to the kingdom, and man judges angels.
Now if you want to meet with God, you have to go through the man Jesus Christ.