2 Thessalonians 1 10
when He comes to be glorified in His saints on that day [that is, glorified through the changed lives of those who have accepted Him as Savior and have been set apart for His purpose], and to be marveled at among all who have believed, because our testimony to you was believed and trusted [and confirmed in your lives].
Compare with other 3 random translations
ASV 2 Thessalonians 1:10when he shall come to be glorified in his saints, and to be marvelled at in all them that believed (because our testimony unto you was believed) in that day.
LSV 2 Thessalonians 1:10when He may come to be glorified in His holy ones, and to be wondered at by all those believing—because our testimony was believed among you—in that day;
NAS 2 Thessalonians 1:10when He comes to be glorified among His saints on that day, and to be marveled at among all who have believed—because our testimony to you was believed.