Faith always needs an object. Think of it in this way: in Africa it is still a common practice for people to send money back home to rural areas when they are in the city. They normally ask someone who is going to their village to bring the money for them. Imagine that you have two people you can ask, and of the two, you are told that the one was given money three times to take it home. The first time when the money was given, R100 was missing, the second time half of the money was missing, and the third time the money did not reach the intended receiver. The second person was also given money three times, and all three times the money was delivered as given to him and on time. Whom will you trust with your money when you have to choose between the two? The more believers see Christ for who he is, what he has done, why he did it, how he did it, the more their faith will grow and be strengthened.
This implies that since Christ is the object of the Christian faith, faith can only grow when Christ is preached truly and completely.
4 since we heard of your faith in Christ Jesus and of the love that you have for all the saints,