In 2 Corinthians 5:20 Paul writes, "Therefore, we are ambassadors for Christ, God making his appeal through us."
An ambassador is a representative of their homeland, king, or president. Christ was an ambassador of the Father, and he represented His Father both by speaking the words of the Father ("...the word that you hear is not mine but the Father's who sent me." John 14:24) and doing the works of the Father ("...the very works that I am doing, bear witness about me that the Father has sent me." John 5:36).
In the same way we are ambassadors of Christ, and we must represent Him both in word and deed.
A few weeks ago I was driving down Route 3 from Augusta to Belfast, and I noticed the car in front of me -- a bright, shiny-red Mustang with two signs printed on the back. The first sign was the name of a driving academy and a telephone number. The second sign had three simple words: "DRIVE THIS MUSTANG!"
It was quite a contrast to the driving academy in my hometown; their cars are nondescript, uninteresting vehicles, and if the academy put a sign on their cars that said, "DRIVE THIS CAR," everyone would laugh.
And I thought, "The car represents the academy in two ways: The sign represents the academy in words, but also, the car itself is a representative of the academy. People who see the Mustang will know all the information they need to contact the academy, but it is the Mustang itself that is the real advertisement. People who see this car will say, "That is the academy I want to go to!"
In the same way, we must be the "advertisement" for Christianity both in our words, and in our lives. Our words tell others about salvation which is to be found only in Christ. But our lives must be an advertisement for Christianity as well; when people look at our lives, they ought to say, "That's a life that's a cut above the rest, and if that's what Christianity is, I want that!"
The words and the deeds must go hand in hand. One without the other is pointless.