when he comes to be glorified in his saints, and to be admired among all those who have believed (because our testimony to you was believed) in that day.
and to be admired in all them that believe (because our testimony among you was believed) in that day: The word "admired" (thaumazo) means "to wonder, wonder at, marvel" (Thayer 284-1-2296). The expressions "that believe" and "was believed" are from the Greek (pistuo) and are used especially of the faith that a man embraces. "Jesus, that is a conviction, full of joyful trust, that Jesus is the Messiah-the divinely appointed author of eternal salvation in the kingdom of God, conjoined with obedience to Christ" (Thayer 511-2-4100). The parenthetical portion of verse 10 ("because our testimony among you was believed") means the believers in Thessalonica are a part of the New Testament church because they have received the testimony of the Apostle Paul, addressed to them by the Holy Spirit through Paul. The word "day" (heemera) means "of the last day of the present age" (Thayer 278-2-2250).