'Letters' in the Bible

Do we begin again to recommend ourselves, except we need, as some, letters of recommendation unto you, or from you?

and if the ministration of the death, in letters, engraved in stones, came in glory, so that the sons of Israel were not able to look stedfastly to the face of Moses, because of the glory of his face -- which was being made useless,

that I may not seem as if I would terrify you through the letters,

because the letters indeed -- saith one -- are weighty and strong, and the bodily presence weak, and the speech despicable.'

This one -- let him reckon thus: that such as we are in word, through letters, being absent, such also, being present, we are in deed.