Romans 1:15

That is why I am so eager to preach the gospel also to you who are at Rome.

(v15, NIV)

Who is Paul eager to preach the gospel to? Paul is obligated to Greeks and barbarians, to the wise and the foolish. He is debtor not to God but to everyone because he did not deserve the free gift of grace which he received. However, he is still talking to the believers who are at Rome. So, he is eager to preach the gospel to the believers at Rome. It is true that he will preach the gospel to non-believers. However, the gospel is to be preached to believers.

Why would you preach the gospel to believers? Don't the believers already have the gospel? Well, if you go to church one day and the preacher is preaching the gospel, do you instantly shut off your brains thinking he's not talking to you? Do you say to yourself, "He's preaching the gospel, this must be directed to all the unbelievers who happen to have attended church today"? As true followers of the Lord Jesus Christ, we should never grow tired or weary or bored of this great gospel which he has graced us with. We should live in it and delight in it.

Looking back to previous verses, Paul is interested in mutual encouragement among these brothers. In addition, he wishes to bring about the obedience which comes from faith among these believers. Yes, the gospel is for the lost, but it is also for those who have been graciously saved by this glorious gospel of grace.