Just came across this one again:
And by letter here he means the Law which punishes them that transgress; but by spirit the grace which through Baptism gives life to them who by sins were made dead.
And what does this mean? In the Law, he that has sin is punished; here, he that has sins comes and is baptized and is made righteous, and being made righteous, he lives, being delivered from the death of sin.
The Law, if it lay hold on a murderer, puts him to death; the Gospel, if it lay hold on a murderer, enlightens, and gives him life.
And why do I instance a murderer? The Law laid hold on one that gathered sticks on a sabbath day, and stoned him. Numbers 15:32-36 This is the meaning of, the letter kills. The Gospel takes hold on thousands of homicides and robbers, and baptizing delivers them from their former vices. This is the meaning of, the Spirit gives life.
The former makes its captive dead from being alive, the latter renders the man it has convicted alive from being dead.
For, come unto me, you that labor and are heavy laden, Matthew 11:28 and, He said not, 'I will punish you,' but, I will give you rest. For in Baptism the sins are buried, the former things are blotted out, the man is made alive, the entire grace written upon his heart as it were a table.
St. John Chrysostom, unpacking 2 Corinthians 3:6 The letter killeth but the spirit giveth life.