'Letters' in the Bible

Are we beginning to commend ourselves again? Or do we need, as some, letters of commendation to you or from you?

But if the ministry of death, in letters engraved on stones, came with glory, so that the sons of Israel could not look intently at the face of Moses because of the glory of his face, fading as it was,

for I do not wish to seem as if I would terrify you by my letters.

For they say, “His letters are weighty and strong, but his personal presence is unimpressive and his speech contemptible.”

Let such a person consider this, that what we are in word by letters when absent, such persons we are also in deed when present.