Faith alone in Jesus Christ’s finished work.

Luke 23 “42 Then he said, “Jesus, remember me when you come into your kingdom.” 43 Jesus answered him, “Truly I tell you, today you will be with me in paradise.””

the thief only believed to be saved.

Acts 16 ” 30 He then brought them out and asked, “Sirs, what must I do to be saved? 31 They replied, “Believe in the Lord Jesus, and you will be saved”

Only one thing is needed: Believe

Luke 10 “41 “Martha, Martha,” the Lord answered, “you are worried and upset about many things, 42 but few things are needed—or indeed only one. Mary has chosen what is better, and it will not be taken away from her.””

John 3 “16 For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. “

Believing in Jesus means to not try to do works for salvation.

Romans 4 “4 Now to the one who works, wages are not credited as a gift but as an obligation. 5 However, to the one who does not work but trusts God who justifies the ungodly, their faith is credited as righteousness. 6 David says the same thing when he speaks of the blessedness of the one to whom God credits righteousness apart from works:
7 “Blessed are those
whose transgressions are forgiven,
whose sins are covered.
8 Blessed is the one
whose sin the Lord will never count against them.
God will credit righteousness—for us who believe in him who raised Jesus our Lord from the dead. 25 He was delivered over to death for our sins and was raised to life for our justification.”

We are saved by faith because works cannot save us.
The only thing that saves us is faith in the death and resurrection of Jesus Christ.

Ephesians 2 “4 But because of his great love for us, God, who is rich in mercy, 5 made us alive with Christ even when we were dead in transgressions—it is by grace you have been saved. 6 And God raised us up with Christ and seated us with him in the heavenly realms in Christ Jesus, 7 in order that in the coming ages he might show the incomparable riches of his grace, expressed in his kindness to us in Christ Jesus. 8 For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— 9 not by works, so that no one can boast.”

The entire purpose of the Bible is that we believe in Jesus to be saved.

John 20 “blessed are those who have not seen and yet have believed…. these are written that you may believe that Jesus is the Messiah, the Son of God, and that by believing you may have life in his name.”

That is enough for me.
It is finished.