'Letter' in the Bible

You are our letter [of recommendation], written in our hearts, recognized and read by everyone.

You show that you are a letter from Christ, delivered by us, written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts.

He has qualified us [making us sufficient] as ministers of a new covenant [of salvation through Christ], not of the letter [of a written code] but of the Spirit; for the letter [of the Law] kills [by revealing sin and demanding obedience], but the Spirit gives life.

For even though I did grieve you with my letter, I do not regret it [now]; though I did regret it —for I see that the letter hurt you, though only for a little while—