because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. Romans 10:9-10 ESV   Doctrine matters, context matter Romans 9-10 are the biggest argument against the sinners prayer. We have many people deceived into thinking they have truly been saved with out a change of heart because someone said you believe in him then your saved. Romans makes it clear that the change in your heart and full acceptance of Jesus as your Lord(meaning ruler of your life, he gets to dictate how we live our lifes) is what justifies us for salvation. Scripture interprets Scripture Matthew 10:32–34 (ESV): So everyone who acknowledges me before men, I also will acknowledge before my Father who is in heaven, 33 but whoever denies me before men, I also will deny before my Father who is in heaven. When in Romans says confessing one is saved or into salvation think of Matthew 10: 32-34 that's the context of the thought behind confessing(acknowledging) other wise Jesus and Isaiah wouldn't say: Mark 7:6–8 (ESV): And he said to them, “Well did Isaiah prophesy of you hypocrites, as it is written, “ ‘This people honors me with their lips, but their heart is far from me; 7 in vain do they worship me, teaching as doctrines the commandments of men.’ 8 You leave the commandment of God and hold to the tradition of men.” This is the issue we have in the church/Christian community were many are unknowgly being lead into hypocritical life's of seeking a feeling or comfort from their continual rebellion.." God knows my heart" or "I profess my religious beliefs therefore I am saved" This may be very well so for those who truly know our Lord and savior and I am in no way unvalitating that because only you yourself and God knows the truth, by breaking this down im inviting anyone reading this to do a heart inventory and to privately come to the conclusion with the help of the Holy Spirit. There will come a day when no one will have a chance to do this- Matthew 7:22–23 (ESV): On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ 23 And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’ I pray that this would help strengthen your desire to know our Lord and his word more and have a zeal for the things of God. God has given us the grace and mercy to come to him and walk with him and spread him to others with the right heart he will accept us with Jesus inputted righteousness giving us to right for forgiveness and salvation, not based on works or anything anyone else says. We do work because we are saved and want to please the father not the other way around.