The Apostle Paul
2 Thessalonians 1:10ESV·traditional attribution

when he comes on that day to be glorified in his saints, and to be marveled at among all who have believed, because our testimony to you was believed.

John Calvin Reformed @genevareformer

10 When he shall come to be sanctified. As he has hitherto discoursed as to the punishment of the wicked, he now returns to the pious, and says that Christ will come, that he may be glorified in them; that is, that he may irradiate them with his glory, and that they may be partakers of it.

Matthew Henry Presbyterian @wholebiblehenry

Having mentioned their persecutions and tribulations, which they endured principally for the cause of Christ, the apostle proceeds to offer several things for their comfort under them; as, I. He tells them of the present happiness and advantage of their sufferings, Th2 1:5. Their faith being thus tried, and patience exercised, they were improved by their sufferings, insomuch that they were counted worthy of the kingdom of God.

Commenting on 2 Thessalonians 1:5-10

John Gill Reformed Baptist @doctorgill

When he shall come to be glorified in his saints,.... Or by them who are set apart for holiness and happiness by God the Father; whose sins are expiated by the blood and sacrifice of Christ; to whom he is made sanctification; and who are sanctified by the Spirit and grace of God; and in whom Christ has a peculiar interest, through his Father's gift...