The Hand of God

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That the Lord is concealed behind some kind of barrier is borne out by many painting and stelae from churches and cemeteries in the early centuries of Christianity. God is never completely visible but only his arm can be seen as it is stretched out from behind a veil, a curtain, a cloud, or a screen, such as in the churches of Nola, SS. Cosa e Damiano in Milan; Sant'Apollinare in Classe, Ravenna, Italy; Parezo in Istria, and others. Even though the correct interpretation may elude the modern churchgoer, it is evidently an ancient symbol of great significance and transcendent reality.
The imagery of the atonement is there as the children of Israel were brought out of Egypt. Thus Moses: "But because the Lord loved you, and because he would keep the oath which he had sworn unto your fathers, hath the Lord brought you out with a mighty hand, and redeemed you out of the house of bondmen, from the hand of Pharaoh" (Deuteronomy 7:8).

Also See:
Power in the Right Hand
The Hand of God