But you are a chosen race, a royal priesthood, a holy nation, a people for God's own possession, that you may show forth the excellencies of him who called you out of darkness into his marvelous light:

 Here is timeless truth. Whether we like it or not, every Christian is an advertisement for Christianity; by his life he either commends it to others or makes them think less of it. The strongest missionary force in the world is a Christian life. 