Answer:
“You are our letter, written on our hearts, known and read by all, shown to be a letter of Christ... written not in ink but by the Spirit of the living God." (2 Corinthians 3:2-3) means:
The saints who are now transformed by the Spirit of God, the product and result of the gospel the apostles preached and have become dear and recommendable by the apostles are now the Bible(epistle) that people see and read.
This particular passage reveals:
1. The people that received transformation- the saints
2. The power behind their transformation - the Spirit of God
3. The preachers that brought the transformation - the apostles
4. The product (result) of their transformation - they became epistles read by all
