Romans 15:17-19 meaning

In this letter to the Romans, we have learned that walking in faith results in living righteously before God. To live righteously is to walk consistently with God's design for us to live in love and service to one another. To be able to walk in faith we must first receive the free gift of God's grace by faith. That is the beginning faith in the phrase found in this letter's theme verse "from faith to faith" (Romans 1:16-17). 

But while that initial faith is what brings us the gift of a resurrected life, our opportunity to experience that gift worked out in our daily existence requires a living faith each day. This is the second faith in the phrase "from faith to faith." In these verses, Paul emphasizes that in light of his calling to take the gospel to the Gentiles, he has reason to boast: Therefore in Christ Jesus I have found reason for boasting in things pertaining to God (v 17). 

Thankfully our behavior does not affect the work Jesus did on the cross, purifying sin and justifying us before God—the result of initial faith. But Paul's teaching and admonition in this letter make it clear that each day we may choose whether or not to live by faith. When we walk in faith we follow God's ways, and in doing so we glorify God to others by being a living sacrifice to God (Romans 12:1).

Paul explains that his boasting is not for any of his accomplishments, but because of what God has accomplished through him. 

He says further, I will not presume to speak of anything except what Christ has accomplished through me (v 18). In another of Paul's letters, his letter to the Galatians, he also speaks of boasting. Galatians 6:13-15 says:

"For those who are circumcised do not even keep the Law themselves, but they desire to have you circumcised so that they may boast in your flesh. But may it never be that I would boast, except in the cross of our Lord Jesus Christ, through which the world has been crucified to me, and I to the world. For neither is circumcision anything, nor uncircumcision, but a new creation."

It is clear that there is no reason to boast in any human action apart from the work of the Spirit. Even if we follow the law, we still break some part of it, as Paul notes in Galatians. 

The only thing to boast in is Christ. Since we are filled with the resurrection power of Jesus when we first believe, we ought to live each day exercising that resurrection power. God's calling for Paul to take the gospel to the Gentiles has resulted in the obedience of the Gentiles by word and deed, in the power of signs and wonders, in the power of the Spirit; so that from Jerusalem and round about as far as Illyricum I have fully preached the gospel of Christ (vv 18-19). 

Many Gentiles have now receive the gift of being born again and are following God in faith. This is a reason to boast in Christ. Paul is proud that the Gentiles are walking in obedience to God. They are both following God's ways in what they say (word) as well as what they do (deed). 

Paul recognizes that he was used by God to take the gospel to the Gentiles, and through him, God performed signs and wonders by the power of the Holy Spirit. Paul does not lift up himself in this. Rather, Paul lifts up the power of the Holy Spirit. 

There are several times that miracles or signs performed through Paul are mentioned in the Bible. Acts 13:11 mentions a miracle at Cyprus, Acts 14:3 a sign at Iconium, Acts 14:8-10, 19-20 a miracle at Lystra, Acts 19:11-12 a miracle at Ephesus, Acts 20:9-12 a miracle at Troas, and Acts 28:1-8 a miracle at Malta.

Hebrews 2:4 says: 

"God also testifying with them, both by signs and wonders and by various miracles and by gifts of the Holy Spirit according to His own will."

God uses signs and wonders to verify the apostles and their word. The purpose of the signs and wonders performed through Paul was to advance the gospel.

Paul explains the extent geographically that he has preached the gospel. Illyricum corresponds to modern day Croatia—Paul preached the gospel in Jerusalem, and in all the regions spreading out from it as far as Illyricum. We will find out later in this chapter that there was no further place for Paul in this region and he planned to travel to Spain next.

Paul is encouraging the believers in Rome by reminding them of the gospel message and to continue their righteous living together (Romans 15:14-16). One of the reasons he is writing to them and admonishing (encouraging) them is because it is his job as a minister. Paul makes it clear that his ministry is found in Christ, God the Father, and the Holy Spirit. He states that while he is a minister to the Gentiles (non-Jews), it is God who gets the credit when the Gentiles obey Paul's teaching. 

It is Christ working through Paul, along with the power of the Holy Spirit, who deserve the credit for the growth and maturation that happens through the gospel. In this, Paul makes clear that he does not desire to receive the praise of men. Rather, his goal is to gain the praise of God for his faithfulness (Romans 2:6-7, 14:10-12).