'Letters' in the Bible

Are we beginning to commend ourselves again? We don't need letters of recommendation to you or from you as some other people do, do we?

But if the ministry that produced death -- carved in letters on stone tablets -- came with glory, so that the Israelites could not keep their eyes fixed on the face of Moses because of the glory of his face (a glory which was made ineffective),

I do not want to seem as though I am trying to terrify you with my letters,

because some say, "His letters are weighty and forceful, but his physical presence is weak and his speech is of no account."

Let such a person consider this: What we say by letters when we are absent, we also are in actions when we are present.