St. Paul - the Spirit and the Letter II Corinthians Ch. 3 (Douay-Rheims):

(- from http://drbo.org/lvb/chapter/54003.htm)

5 Not that we are sufficient to think any thing of ourselves, as of ourselves: but our sufficiency is from God.

6 Who also hath made us fit ministers of the new testament, not in the letter, but in the spirit. For the letter killeth, but the spirit quickeneth.

[Vulgate: 5 non quod sufficientes simus cogitare aliquid a nobis quasi ex nobis sed sufficientia nostra ex Deo est 6 qui et idoneos nos fecit ministros novi testamenti non litterae sed Spiritus littera enim occidit Spiritus autem vivificate ]