Ambrose of Milan : Who, then, is the Lord Who makes us to increase and abound before God and our Father at the coming of the Lord Jesus? He has named the Father and has named the Son; Whom, then, has he joined with the Father and the Son except the Spirit? Who is the Lord Who establishes our hearts in holiness. For holiness is a grace of the Spirit, as, too, is said farther on: "In holiness of the Spirit and belief of the truth." — On the Holy Spirit, Book 3, Chapter 14, 95 Ambrosiaster : At this place, the foreknowledge of God resounds, because He knows the minds of all before their birth; and He is not unaware of those who will believe. Therefore, from the beginning, he knows that these faithful ones will be, who, by believing, make an increase of faith, not a detriment; for, being sanctified through the faith of the truth of the Gospel of the Son of God, they are acquired for an increase of the glory of the body of Christ, as he also says in another epistle: that all things may grow unto the increase of God (Colossians 2:19). For whoever, having deserted the devil, take refuge in the faith of Christ, makes an increase for God in the body of Christ, which they had previously caused a detriment. — Commentary on 2 Thessalonians Thietland of Einsiedeln : Yet we must always give thanks to God for you We should note that he had said this at the beginning of the epistle. brothers, beloved of God as if he should say, his unspeakable and immeasurable gifts. But not that those who he said to be about to be loved by God cannot in any way be mistaken. No one, therefore, disputed that they are of great merit; wherefore the Apostle calls them beloved in the judgment of him who can neither deceive nor be deceived. by the sanctification of the Spirit and by faith in the truth He added 'of the Spirit' because this sanctification is in the Spirit and is acquired in the Spirit.