When Paul and the other disciples preached the word of God to the people, They gave the credit, the glory, and thankful joy to Jesus Christ. Instead of saying, "hey guys! Look what I did!". They said, "We constantly are thanking God for what he is doing! He gave you the strength to accept the word he preached through us!" (it's a diffrent translation in the book). But what does that tell us? That if "we" make a diffrence in spreading the word, we can give the credit to Jesus Christ.