Carriers of Christ: by CS Lewis (Mere Christianity)

For we are to God the aroma of Christ among those who are being saved and those who are perishing.  To the one we are the smell of death; to the other, the fragrance of life. And who is equal to such a task?  Unlike so many, we do not peddle the word of God for profit. On the contrary, in Christ we speak before God with sincerity, like men sent from God. 2 Corinthians 2:15-17

Some of you may feel that this is very unlike your own experience. You may say 'I've never had the sense of being helped by an invisible Christ, but I often have been helped by other human beings.' That is rather like the woman in the first war who said that if there were a bread shortage it would not bother her house because they always ate toast. If there is no bread there will be no toast. If there were no help from Christ, there would be no help from other human beings. He works on us in all sorts of ways: not only through what we think our 'religious life'. He works through Nature, through our own bodies, through books, sometimes through experiences which seem (at the time) anti-Christian. When a young man who has been going to church in a routine way honestly realises that he does not believe in Christianity and stops going—provided he does it for honesty's sake and not just to annoy his parents—the spirit of Christ is probably nearer to him then than it ever was before. But above all, He works on us through each other.

Men are mirrors, or 'carriers' of Christ to other men. Sometimes unconscious carriers. This 'good infection' can be carried by those who have not got it themselves. People who were not Christians themselves helped me to Christianity. But usually it is those who know Him that bring Him to others. That is why the Church, the whole body of Christians showing Him to one another, is so important. You might say that when two Christians are following Christ together there is not twice as much Christianity as when they are apart, but sixteen times as much.