'Letter' in the Bible

That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.

Therefore, brothers, stand firm and hold to the traditions you were taught, either by our message or by our letter.

And if anyone does not obey our instruction in this letter, take note of that person; don’t associate with him, so that he may be ashamed.

This greeting is in my own hand—Paul. This is a sign in every letter; this is how I write.