Which has come to you, just as in all the world also it is constantly bearing fruit and increasing, even as it has been doing in you also since the day you heard of it and understood the grace of God in truth. (Colossians 1:6 NASB)
The gospel is said to bear fruit and increase constantly. This implies that the gospel has produced something that can bear fruit and increase in some way. Paul is thankful for the Colossian believer's faith and their love for each other and it is due to the gospel that they had believed which is based on the hope found in Jesus Christ alone.
The gospel is called "the word of truth," it is also referred to as "the grace of God in truth."
What is the gospel?
It is the power of God unto salvation for all the believing ones as it says in Romans 1:16. It is the good news of victory that Jesus Christ has over death and sin. When Christ rose from the grave, God proved to the world that He had accepted Christ's sacrifice for sin and He now has a glorified, resurrected body. Our hope for eternity and our future resurrected body rests fully in Christ and His finished work on the cross.
The gospel is the good news that salvation and right standing before God has come to mankind and it is on the basis of the shed blood of Christ. The gospel in the Greek culture was the good news of victory proclamation that would be carried out after a major victory in battle. Christ's resurrection and the proclamation of His gospel to the world is the sounding forth of victory over Satan, sin, and death that Christ has accomplished.
The gospel is by the grace of God. It is a gospel of unmerited favor by God towards sinful man. The only thing we contribute to salvation is the sin that makes it necessary to have a payment for that sin.
What kind of gospel?
The gospel is a universal gospel. It transcends all nationalities, races, cultures, etc. There is no Jew or Greek in Christ only faith. Nothing about our family, our status in society or anything else makes us qualified to receive salvation. Only by God's grace and on the basis of our faith in Christ do we receive eternal life.
This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come. (Matthew 24:14 NASB)
This verse in Matthew among many others like it make it clear that the gospel is for the whole world including all people. This does not mean literally every single individual because not 100% of mankind will receive eternal life by the grace of God. Many will reject Christ, choose their sin, and die in their sin. So, for them the gospel is not good news but is a news of condemnation which they are already under. Take John 3:17-18 into consideration:
For God did not send His Son into the world to judge the world, but that the world might be saved through Him. He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God. (John 3:17-18 NASB)
God did not send Christ into the world through the incarnation to judge the world. The world, mankind stands in judgment based on his sin even if Christ never entered into His own creation. In fact, without the incarnation, without the shed blood of Christ, without payment for sin, 100% of the entire population of mankind would populate hell. None would be saved from hell's fire.
Christ's coming into the world is to redeem His elect people, to provide the atonement for His people, His believing ones. Those who do not believe and have faith in Christ are not judged because they failed to believe in Christ. They are judged based on their own sin. That is what puts them under condemnation. Now, we are commanded to believe in Christ so there is the sin of unbelief. However, there have been statements in that past by some theologians that the only sin that actually sends you to hell is the sin of unbelief.
This is not accurate. Whether or not God enters His creation and provides payment for sin does not change the fact that the whole world stands condemned before God. Christ's entering the world and dying on the cross provides the full payment for sin for the believing ones so that their condemnation is eradicated in the sight of God and He remembers their sin no more.
What does the gospel do?
It bears fruit and increases. Notice in verse 6 of the 1st chapter of Colossians that it refers to the gospel as "constantly bearing fruit and increasing." Notice what the book of Acts says in chapter 9:
So the church throughout all Judea and Galilee and Samaria enjoyed peace, being built up; and going on in the fear of the Lord and in the comfort of the Holy Spirit, it continued to increase. (Acts 9:31 NASB)
The gospel first bears fruit in a person's life when God regenerates them unto saving faith and they are made a new creature in Christ. From that point forward the saved sinner is to be continually sanctified in Christ, pursuing holiness and righteousness as the gospel continues to bear its fruit in their life. The gospel will finish its work in the saved believer when the consummation of all things is completed at Christ's return and the believer is ushered into eternity with Christ with a glorified body.
The gospel also sees fruit and increase in the numeric growth of the church. As the gospel inwardly transforms believers they are able to image Christ in the world and as they grow in spiritual maturity they are better equipped to carry the gospel out to the world and the Holy Spirit will continue to draw the elect from the four corners of the earth to God and the church will increase.
What does the gospel produce?
The gospel produces servants of Christ.
Just as you learned it from Epaphras, our beloved fellow bond-servant, who is a faithful servant of Christ on our behalf, and he also informed us of your love in the Spirit. (Colossians 1:7-8 NASB)
The gospel which they learned in Colossae from Epaphras had produced servants of Christ in their church. The gospel always 100% of the time produces obedient servants of Christ.
The Greek word translated servant in verse 7 is the same word diakonos translated deacon and even minister elsewhere in the New Testament. What this means is that no matter what role a Christian has in the church, whether pastor, or deacon, or lay-person; we all are servants of Christ. We serve the most high God!
There are no servants of pastors or servants of deacons, only servants of Christ. The gospel saves! The gospel transforms! The gospel bears fruit and increases the church! The gospel produces servants of Christ!
Are you serving Him? Are you dying to self daily? Are you pursuing righteousness and holiness? Are you submitting yourself to the Word of God and to the Holy Spirit of God?
The regenerated person has the indwelling Holy Spirit and will serve their Lord and Savior, Jesus Christ. This is the hallmark of every believer and it is the 100% guarantee of the gospel of Jesus Christ.