"... at the beginning of the human race the woman was made of a rib taken from the side of the man while he slept; for it seemed fit that even then Christ and His Church should be foreshadowed in this event. For that sleep of the man was the death of Christ, whose side, as He hung lifeless upon the Cross, was pierced with a spear, and there flowed from it blood and water, and these we know to be the sacraments by which the Church is built up."

Source: Saint Augustine of Hippo (2016). “Saint Augustine of Hippo Collection [50 Books]”, p.10392, Aeterna Press