But we are bound to give thanks always to God for you, brethren beloved of the Lord, because God has from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth:
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Ambrose of Milan
AD 397
And the apostle also teaches that the Holy Spirit sanctifies. For he speaks thus, “We are bound to give thanks to God always for you, brothers dearly beloved of the Lord; because God chose you as first fruits for salvation, in sanctification of the Spirit, and belief of the truth.” So, then, the Father sanctifies, the Son also sanctifies, and the Holy Spirit sanctifies; but the sanctification is one, and the grace of the sacrament is one. –.
How unto salvation? By sanctifying you through the Spirit. For these are the things that are the efficient causes of our salvation. It is nowhere of works, nowhere of righteous deeds, but through belief of the truth. Here again, in is used for through. And through sanctification of the Spirit, he says,
With these words they show that they were converted to faith by his teaching. The purpose was for the acquisition of the glory of our Lord Jesus Christ. As if he should say, "Therefore you were drawn to the faith by our teaching, so that you might obtain for yourselves the glory of the Lord."