One of the common misconceptions regarding the identity of “who is a Christian” is the belief that being Christian is about what you do.
Many people believe that select good works outweigh bad behavior, and that God is looking for those good works to consider one worthy for heaven, or His favor.
It’s true that the bible is full of instructions about behavior. There are hundreds of rules in Old Testament law relating to Israel specifically and many more in the New Testament, relating to Christian behavior. However, none of these prescribed behaviors was intended to bring an individual into a right relationship with God. Rather, they were given as a model of behavior for those already in a right relationship with God.
Here is what Jesus said about the subject, and mind you, He spoke this to one of the nations top religious leaders… someone we might consider a very “good” man:
Jesus answered and said to him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.” -John 3:3
This was part of a conversation with Nicodemus, it would be good to read the entire conversation in John 3 to get an idea of all that Jesus said. Repeatedly in the conversation Jesus pointed to this concept of having a spiritual transformation from within, which He referred to as being “born again.” He actually made it clear that short of that, one could not “see the kingdom of God” nor could they “enter the kingdom of God” (John 3:5).
Since Jesus is the Christ, the source of our Christian faith, it is important to understand what He Himself said on the matter of who is and is not Christian. He went on, in John chapter 3, to direct Nicodemus to the one thing he needed to do, to unlock, as it were, this idea of rebirth:
“…so that whoever believes will in Him have eternal life. For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.” -John 3:15-16*
The Apostle Paul confirmed this teaching, explaining that salvation is by faith in Jesus: “Therefore, having been justified by faith, we have peace with God through our Lord Jesus Christ, -Romans 5:1*
To be a Christian, one must believe in the person and work of Jesus Christ, relying on Him and Him alone for salvation. Good works are just that, good works, but they cannot cause you to be born again.
Billy Graham has a great video out that clarifies some of these points. You can watch it online here: https://myhopewithbillygraham.org/program/heaven/
* all scripture is NASB and emphasis is mine