John Calvin on Romans 11:14

14. And save, etc. Observe here that the minister of the word is said in some way to save those whom he leads to the obedience of faith. So conducted indeed ought to be the ministry of our salvation, as that we may feel that the whole power and efficacy of it depends on God, and that we may give him his due praise: we ought at the same time to understand that preaching is an instrument for effecting the salvation of the faithful, and though it can do nothing without the Spirit of God, yet through his inward operation it produces the most powerful effects.