2 Thessalonians 2:13-15

But we ought always to give thanks to God for you, brothers beloved by the Lord, because God chose you as the firstfruits to be saved, through sanctification by the Spirit and belief in the truth. To this he called you through our gospel, so that you may obtain the glory of our Lord Jesus Christ. So then, brothers, stand firm and hold to the traditions that you were taught by us, either by our spoken word or by our letter.