2 Thessalonians 2:13-15 WEB

13 But we are bound to always give thanks to God for you, brothers loved by the Lord, because God chose you from the beginning for salvation in sanctification of the Spirit and belief of the truth;
14 whereunto he called you through our gospel, to the obtaining of the glory of our Lord Jesus Christ.
15 So then, brothers, stand firm, and hold the traditions which you were taught by us, whether by word, or by letter.