Listen to another testimony. All flesh had become corrupt because of its sins. God said: “My Spirit will not remain in human beings, for they are flesh.” God thus shows that spiritual grace is repelled by uncleanness of the flesh and by the stain of more serious sin. So God resolved to restore the gift he had given.

You see the water [of baptism], you see the wood [of the cross], you look on the dove [the Holy Spirit], and you hesitate to believe the mystery? The water is that in which the flesh is dipped, to wash away all its sin. In it all wickedness is buried. The wood is that to which the Lord Jesus was fastened when he suffered for us. The dove is the one in whose likeness the Holy Spirit descended , as you have learned from the New Testament: the Spirit who breathes into you peace of soul, tranquility of mind.

–Ambrose, Bishop of Milan, On the Mysteries 12-16