St. Paul's Second Letter to the Corinthians 2:14-17; 3:1-3
Brethren, thanks be to God, who in Christ always leads us in triumph, and through us spreads the fragrance of the knowledge of him everywhere. For we are the aroma of Christ to God among those who are being saved and among those who are perishing, to one a fragrance from death to death, to the other a fragrance from life to life. Who is sufficient for these things? For we are not, like so many, peddlers of God's word; but as men of sincerity, as commissioned by God, in the sight of God we speak in Christ.
Are we beginning to commend ourselves again? Or do we need, as some do, letters of recommendation, to you, or from you? You yourselves are our letter of recommendation, written on our hearts, to be known and read by all men; and 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.