Paul's belief (faith) did not save him. His fasting did not save him. His prayers did not save him. None of these things washes away sin. Only one thing washes away sin- the blood of Christ- which we get when we are baptized into His death (Romans 6:3).
If Paul's faith did not save him, then he was confused when he wrote Ephesians 2:8,9. We are
Spirit baptized (and not water baptized) into the body of Christ (1 Corinthians 12:13). You are confusing the picture with the reality. The washing away of sin by the blood of Christ is
signified, yet
not procured in the waters of baptism. We are forced to give this interpretation by the context. Before mentioning baptism in chapter 6, Paul had repeatedly emphasized that
faith, not water baptism is the instrumental cause of salvation/justification (Romans 1:16, 3:22-30; 4:4-6, 13; 5:1). That is when the old man was put to death and united in the likeness of His death, which water baptism
symbolizes and pictures.
Ananias said to Paul, "What are you waiting for? Arise, be baptized, and wash away your sins- calling on the name of the Lord."
As Greek Scholar A.T. Robertson explains: As in Romans 6:4-6 where baptism is the picture of death, burial and resurrection, so here baptism pictures the change that had already taken place when Paul surrendered to Jesus on the way.
Baptism here pictures the washing away of sins by the blood of Christ.
We are saved when we obey the gospel- which is the death, burial, and resurrection of Jesus Christ. For when we are baptized, we die to ourself, bury our old sinful self in the watery grave of baptism, and are raised alive with the Holy Spirit. The Holy Spirit is what marks us for salvation.
Again, water baptism is the
picture, but not the reality. We are saved when we obey the gospel and we
obey the gospel by
choosing to believe the gospel (Romans 1:16; 10:16).
(With flames of fire (hell) He will take vengeance on those who know not God, and who obey not the gospel of His Son).
Romans 10:16 - But they have not all
obeyed the gospel. For Isaiah says, "Lord, who has
believed our report?" Refusing to believe the gospel by trusting in the death, burial and resurrection of Christ as the ALL-sufficient means of your salvation is refusing to obey the gospel. The gospel is NOT "water baptized or condemned." That is a "different" gospel.
Baptism is how we get into Christ, but it's possible to come back out.
Spirit baptism (not water baptism) is how we get into the body of Christ when we believe the gospel. Where does the Bible say "come back out" of the body of Christ? Ephesians 1:13 - In Him you also trusted, after you heard the word of truth, the
gospel of your salvation; in whom also, having
believed, you were
sealed with the Holy Spirit of promise, 14 who is the
guarantee of our inheritance until the redemption of the purchased possession, to the praise of His glory. Believers are sealed
unto/for the day of redemption (Ephesians 4:30).
You can't willfully commit any sin you want. The Bible says "If you sin willfully there no longer remains a sacrifice for your sins." 'No longer' means it once genuinely did- which means OSAS (once saved always saved) is a false doctrine. You can lose your salvation- and this verse proves it. (Sinning willfully means premeditated, not tempted in the moment- but preplanned)
In regards to Hebrews 10:26, To "sin willfully" in the Greek carries the idea of deliberate intention that is habitual, which stems from rejecting Christ deliberately. This is CONTINUOUS ACTION - A MATTER OF PRACTICE. Now we don't walk along our daily life and "accidentally" fall into a pit called sin. We exercise our will but, the use of the participle clearly shows a CONTINUOUS ACTION. The
unrighteous practice sin - (1 Corinthians 6:9-10; Galatians 5:19-21);
not the righteous, who are born of God - (1 Corinthians 6:11; 1 John 3:9). OSAS (when properly understood) is not a false doctrine. Hebrews 10:39 - But we are
not of those who draw back to perdition, but of
those who believe to the saving of the soul. Those who
draw back to perdition do not believe to the saving of the soul and those who
believe to the saving of the soul do not draw back to perdition. So there is no loss of salvation here. Only a failure to receive it.
So no, you can't simply believe and then commit any sin you want thinking you can't lose your salvation, because you can.
1 John 3:9 -
No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God. So much for believers committing any sin they want. Show me where the Bible specifically says "lose salvation." It sounds to me like you have been thoroughly indoctrinated into church of Christ (Campbellism) theology.