“But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth: whereunto He called you by our gospel, to the obtaining of the glory of our Lord Jesus Christ.” 2 Thessalonians 2:13-14 (KJV)
We should all be thankful for God choosing us for salvaation – if indeed we have been chosen. How we are chosen, just as all believers are: 1.) Set apart by the work of the Spirit; and 2.) Believing the truth.
It is done by the gospel, and for the purpose of obtaining the glory of Jesus.
These messages to the Thessalonian Church are as much a part of the gospel as the death, burial and resurrection of Jesus. To reject any of the Scriptures is to reject God, Christ Jesus, and eternal life. Receive, and believe the whole gospel or perish.