1 Cor. 12:1-3 (ESV)
Now concerning spiritual gifts, brothers, I do not want you to be uninformed.  You know that when you were pagans you were led astray to mute idols, however you were led.  Therefore I want you to understand that no one speaking in the Spirit of God ever says "Jesus is accursed!" and no one can say "Jesus is Lord" except in the Holy Spirit.
Paul turns his attention to spiritual gifts. It seems there were many Christians that were not informed as to their Spiritual gifts, or their proper use. Some others were guilty of being proud of their gifts, and thinking they were superior for having them. This led others whose gifts were not as apparent to believe that maybe they did not have the Spirit, since they could not speak in tongues. Paul starts right away to comfort these people. He says: “Don’t be led astray… No one can say “Jesus is Lord” except in the Holy Spirit.”
Our confession of faith belies the fact that we have the Holy Spirit. We would not be able to confess Jesus is Lord if we didn’t have the Holy Spirit. In fact our faith is the work of the Holy Spirit. This makes the sinner’s prayer, or making a decision for Christ, and other such neo evangelical ideas pretty silly. You can’t invite Christ into your heart. The moment you can even try to do that, He is already there. The only thing accomplished by this nonsense is a false sense of spiritual achievement, or contribution to your salvation. This is why we don’t ask people to make a decision for Christ. We simply proclaim the gospel. It is true regardless of what they believe. We tell them Christ forgave them there sins, if the Holy Spirit brings them to believe this they will make a confession of faith, but it will be the work of the Holy Spirit, not theirs.
This is the problem with a statement such as “I believe, therefore I am forgiven.” It makes faith a work we do by which we attain forgiveness. The fact is we were forgiven long before we believed. But the Holy Spirit has brought us to believe this, so we confess this, so we proclaim this. Now we need not worry if our faith is strong or weak, whether we have one or another spiritual gift. We have the Holy Spirit, and by His work we are led to faith, and to confession.