Belief in Jesus is more than mere belief. The word means to have an assurance.
Saying a sinners prayer does not save you. Repenting and calling out to Jesus as the tax collector Saves you.
Luke 18:9 - Also He spoke this parable to some who trusted in themselves that they were righteous, and despised others/viewed others with contempt/looked down on everyone else. 10 “Two men went up to the temple to pray, one a Pharisee and the other a tax collector.
*Notice all the upcoming
"I" in verses 11 and 12.
11 The Pharisee stood and prayed thus with himself, ‘God,
"I" thank You that
"I" am not like other men—extortioners, unjust, adulterers, or even as this tax collector. 12
"I" fast twice a week;
"I" give tithes of all that
"I" possess.’
13 And the tax collector, standing afar off,
would not so much as raise his eyes to heaven, but beat his breast, saying, ‘God, be merciful to me a sinner!’ 14 I tell you,
this man went down to his house justified rather than the other; for everyone who exalts himself will be humbled, and he who humbles himself will be exalted.”
*The tax collector demonstrated humility and faith. The Pharisee demonstrated self-righteousness and a lack of faith.
In regard to the sinner's prayer, saying a sinner's prayer will not accomplish anything on its own. I must have prayed the sinner's prayer 20 different times with Pat Robertson while watching the 700 Club back when I was a teenager, yet nothing happened. Why?
Because there was no repentance and faith. Such a prayer needs to include what a person knows, understands, and believes about their sinfulness and need for salvation,
followed by repentance/faith. People need to hear the gospel. Faith comes by hearing, and hearing by the word of God. (Romans 10:17)
For a person who comes to the realization they are lost and in need of Jesus Christ to save them, (Romans 3:23; 6:23) they may obtain salvation
only by grace through faith in Jesus Christ alone (Ephesians 2:8,9). One needs to understand that Jesus Christ, God in human form, took his sins and paid the penalty for his sins by His sacrifice on the cross of Calvary, was buried, and rose again the third day, and they need to make a genuine and willful decision to totally trust in Jesus Christ as the ALL-sufficient means of their salvation. (Romans 1:16)
Now if subsequent to such a decision, the person would like to pray what some call a "sinner’s prayer," (calling on the name of the Lord to save him) he may do so,
as long as he understands that it was his decision to trust in Jesus Christ for salvation that apprehends his salvation and not simply reciting a prayer in of itself. Reciting a prayer, in of itself does not save, as if it's a magical formula to recite a set of words, but prayer may be used to sincerely call upon the name of the Lord. (Romans 10:13)