John Chrysostom

"But the Lord," he says, "direct your hearts into the love of God, and the patience of Christ." Again he commends them, and prays, showing his concern for them. For when he is about to enter upon reproof, he previously smooths down their minds, by saying, "I am confident that ye will hear," and by requesting prayers from them, and by again invoking upon them infinite blessings. …

Homily on 2 Thessalonians 5 ↗

Basil of Caesarea

I am sure that a work done by one or two pious men is not done without the cooperation of the Holy Spirit. For when nothing merely human is put before us, when holy men are moved to action with no thought of their own personal gratification, and with the sole object of pleasing God, it is plain that it is the Lord Who is directing their hearts. …

Letters 229 ↗

Theophylact of Ohrid

Again he prays for them, showing his care for them. Since he intended to reproach some of them, he first softens their hearts, to show that he gives them that instruction out of great love. And so he said: "The Lord direct your hearts," that is, may He cause them to go on the right path and not turn aside from it. For many things lead one astray from the right path of love: both covetousness, and vainglory, and sorrows, and temptations. …

Commentary on 2 Thessalonians ↗

Thomas Aquinas

Then when he says "and may the Lord," he prays for them, saying "may the Lord direct your hearts," namely that you may reach the goal. "It belongs to man to prepare his soul, but to direct the tongue belongs to the Lord" (Prov 16:1). And a little further down it says, "a man's heart arranges his way, but the Lord directs his steps" (Prov 16:9), namely, to his destined reward. …

Commentary on 2 Thessalonians ↗