Surely we do not need, as some do, letters of recommendation to you or from you, do we? You yourselves are our letter, written on our hearts, to be known and read by all; and you show that you are a letter of Christ, prepared 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. -1 Cor 3.1-2
The language of this exhortation, which we know because it is a text, an unnecessary letter, names the Corinthians as the body by which people can come to know Christ. The body of the Corinthians becomes a virtual letter of Christ, just as Paul's letter to the Corinthians becomes a virtual body. The exchange of encouragement occurs in the passing of letters from Paul to his congregations, but the logic of these interstices is a bodily one.