John Chrysostom

"Because our testimony unto you was believed in that day." That is, when those are brought into public view, who have suffered unnumbered ills, designed to make them apostatize from the faith, and yet have not yielded, but have believed, God is glorified. Then is shown the glory of these men also. "Judge none blessed," it says, "before his death." On this account he says, in that day will be shown those who believed.

Homily on 2 Thessalonians 3 ↗

Theophylact of Ohrid

When the people who now oppose the Gospel and exalt themselves see that those whom they tormented have become partakers of endless glory, then the glory of God will be openly revealed. For their glory is His glory, so that by the very means through which He glorifies the saints, He Himself is also glorified. Just as His wealth consists in the fact that there are faithful ones, so also His glory consists in the fact that there are such people who will enjoy His blessings. That is, through those who believed. …

Commentary on 2 Thessalonians ↗

Thomas Aquinas

Then when he says, "when he shall come," he treats of the saints' reward. And first, he sets out the reward; second, the merit of the saints, at "those who have believed." He commends the glory of the saints as regards its essence, a participation in the glory of God, when he says "to be glorified"; and as regards its overflow, at "and to be made wonderful." He says, therefore, "when he shall come." Christ is most certainly glorious; "that every tongue may confess that the Lord Jesus Christ is in the glory of God the Father" (Phil …

Commentary on 2 Thessalonians ↗