Prologue.
prologue.2 14. Let us then not keep the Lord's money buried and hidden in the flesh; nor let us hide our one talent in a napkin; but like good money-changers let us ever weigh it out with labour of mind and body, with an even and ready will, that the word may be near, even in your mouth and in your heart.
15. This is the word of the Lord, this is the precious talent, whereby you are redeemed. This money must often be seen on the tables of souls, in order that by constant trading the sound of the good coins may be able to go forth into every land, by the means of which eternal life is purchased. “This is eternal life,” which Thou, Almighty Father, givest freely, that we may know “You the only true God, and Jesus Christ Whom You have sent.”
Source: On the Christian Faith (De fide) (New Advent)