In Acts 15, we a dispute going in the church where certain men from Judea were preaching to the Gentiles (non-Jewish folk), “Unless you are circumcised according to the custom of Moses, you cannot be saved" (Acts 15:1). Circumcision was the outward sign for the Jewish people indicating they belonged to the people of God. They came to faith in Christ without performing the sign of circumcision because Christ nullified that sign by His finished work on the cross and gave us the Holy Spirit. Baptism by immersion after belief was that exterior sign yet these men were teaching faith in Christ is not enough. The church came together in Jerusalem to settle this matter and they came to the conclusion they should force any believer that was not a Jew to contribute to an exterior work showing they are saved.
As I was thinking about this passage, the thought occurred to me that there are many Christians who like to add on to salvation. They believed they are saved by faith yet they add on some rules. There are times in my life, I have added on some rules so I may show others that I am saved, but I was focusing on my exterior actions versus the interior work the Holy Spirit was doing in me. Yes, Paul tells to work out our salvation with fear and trembling (Philippians 2:12-13) and James says that faith without works is dead (James 2:14-26). We are show we are saved by what we do as a response of the finished work of Christ. So why do we add on to salvation? Here are my opinions as to why Christians (pastors, teachers, elders, deacons, laity, etc.) want to give people a Jesus + Something = Everything mentality in regards to salvation.
First, control. Legalism is a way of controlling someone. When one comes to faith in Christ we rejoice but we want to keep them there so we give them rules. Don't watch these kinds of movies, tuck in your shirt, and the only music you can listen to is the Gaither Vocal Band. You can also add use this translation of the Bible or to hell with you. Control is not just on someone else, but it is also on ourselves. I use to be one of those people that say Christians can only listen to non-Christian music, which is another post for another time. I thought if I listen to this music, God will not take away my salvation. Bad theology I know. Praise God I don't think that way anymore.
Second, we don't have faith in God's grace. We have that God will save us but we lack in His grace to sustain us. We lack the faith that His grace will teach us to renounce godlessness and worldly passions. We also lack faith in His grace that we must tell others that they must do this and that in order to be saved.
Third, because we don't have faith in the grace of God, we lack confidence in the finished work of Christ. We love that Jesus died for our sins, but we want to contribute to His work to make sure we are saved. People who want to add to salvation have no faith that God's wrath and punishment was poured out on Jesus, therefore, they want to be sure they are in the clear.
Fourth, because they have no confidence in the finished work of Christ, they don't trust God completely. Normally, when we think of trusting in God, we think of getting our of difficult circumstances, which is true, we must trust Him in that regards. However, we also must trust God that He did what He said He would do by providing a Messiah to take away the sins of the world. We also must trust in the Bible that when it says, "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast" (Ephesians 2:8-9), God meant it. We are saved not of our own doing but by His grace.
Finally, because they don't trust God, they think grace is to easy. Every other religion says we must do, but Christianity says it is done because of Christ's finished work on the cross. Sounds easy right? This must be a man-made religion. If Christianity was a man-made religion, why do we have one way to salvation instead of multiple ways. Grace is God's unmerited favor to sinners who respond to the gospel and God gives mercy on those who call upon the name of the Lord. We don't have to make a journey to a holy city or pray to dead saints. We call upon the living God.
Christians, salvation is a free gift to us by God at the cost of His Son's life. We do not need to add to it. That is what was one of the issues the early church wrestled with. If you struggle in this thinking that you must contribute to your salvation, I invite you to read the entire book of Galatians in the Bible, which the Apostle Paul addressed this very some topic to the church.