Matthew 7:20–21, New King James Version

“Jesus said, ‘Therefore by their fruits you will know them. Not everyone who says to Me, ‘Lord, Lord,’ shall enter the kingdom of Heaven, but he who does the will of My Father in Heaven.’”

What makes a person a Christian? Going to church or doing good deeds do not necessarily make a person a Christian. Does sitting in your garage make you a car or sitting in the produce section at the store make you fruits or vegetables?

Knowing if someone is a Christian involves observing evidence of a transformed life, rather than just their claims or church attendance. This includes love for others, fruit of the Spirit (joy, peace, patience, kindness), reliance on God, a desire to follow Jesus' teachings, and a commitment to repentance, though they will not be perfect. 

Some core characteristics of a Christian are, first, the fruit of the Spirit: Galatians 5:22-23 defines this as love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control.

If a person does not show any fruit—that is, any visible evidence of the change that has taken place in his heart since receiving Jesus Christ as his personal Savior—then that individual is not a Christian. 

Secondly, love for others: As Jesus said, "By this all will know that you are my Disciples, if you have love for one another," (John 13:35, NKJV)---meaning a person thinks of others before themselves.

Next is a transformation of life: A genuine Christian is changed internally, often shown through a desire for holiness, repentance when falling into sin, and a decrease in desire for worldly, selfish living.

A true Christian trusts in Jesus Christ; They believe they are saved by grace through faith in Jesus alone, rather than by their own good works.

Obedience to God's Word: A desire to understand, follow, and live according to the teachings of the Bible is another characteristic of a true Christian. They handle problems and issues of life in a biblical way.

We have to be careful and test the spirits and use discernment when trying to see if a person is a true Christian. 

Signs of Genuine Faith vs. Superficiality:

True Christians possess a genuine hunger for God's word and prayer, not just out of duty or to look "good'.

Repentance: A Christian is not perfect, but they will not be comfortable in continued, habitual sin.

Humility: They recognize they are sinners in need of grace and treat others with love rather than holding themselves as superior. 

Ultimately, while behavior provides evidence, only God truly knows a person's heart. 

More depends on a person's walk than their talk. My prayer for all of us is that we will walk in such a way that the world can know we are Christians.