Romans 5:1 ESV “Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ.”
Hebrews 11: ESV “Now faith is the assurance of things hoped for, the conviction of things not seen.”
So what does it really come down to when we talk about “being a christian”: Faith and Repentance or another way of putting it, trusting and obeying God’s word. Where do I get this? Ecclesiastes: 12:13b ESV “…Fear God and keep his commandments, for this is the whole duty of man.”
In the booklet, “For Your Joy”, John Piper has summarized this on page 36:
“The benefits purchased by the death of Christ belong to those who repent and trust him.
“Repent” means to turn from all the deceitful promises of sin. “Faith” means being satisfied with all that God promises to be for us in Jesus. “He who believes in me,” Jesus says, “shall never thirst” (John 6:35). We do not earn our salvation. We cannot merit it (Romans 4:4-5). It is by grace through faith (Ephesians 2:8-9). It is a free gift (Romans 3:24). We will have it if we cherish it above all things (Matthew 13:44). When we do that, God’s aim in creation is accomplished: He is glorified in us and we are satisfied in Him- forever.”