phil 1:6

. St. Augustine. The text of St. Augustine (De gratia et libero arbitrio, chap. 17) reads thus: “God Himself works so that we may will at the beginning what, once we are willing, He cooperates in perfecting; therefore does the Apostle say: ‘Being confident of this very thing, that He who hath begun a good work in you, will perfect it unto the day of Christ Jesus’ (Phil. 1:6). That we should will therefore, He accomplishes without us; but when we do will, and so will as to do, He cooperates with us.

[quoted here http://www.ewtn.com/library/theology/grace4.htm}