Therefore, brethren, stand fast, and hold the traditions which you have been taught, whether by word, or our epistle.
All Commentaries on 2 Thessalonians 2:15 Go To 2 Thessalonians 2
John Chrysostom
AD 407
Hence it is manifest, that they did not deliver all things by Epistle, but many things also unwritten, and in like manner both the one and the other are worthy of credit. Therefore let us think the tradition of the Church also worthy of credit. It is a tradition, seek no farther. Here he shows that there were many who were shaken.