Yes, Christianity is personal. Religion has to be personal—Jesus Christ is a person. He loves people. That is personal. But after it becomes personal it must become public.
How does Jesus expect the personal to become public? “What I tell you in the dark [personal], speak in the daylight [public]; what is whispered in your ear [personal] proclaim from the roofs [public]” (Matt. 10:27).
If you do not want to be publicly identified with Jesus now, then He will not identify with you publicly later. “If anyone is ashamed of me and my words, the Son of Man will be ashamed of him when he comes in his glory and in the glory of the Father and of the holy angels” (Luke 9:26).
Christianity is not personal in a private way. Christianity is personal in a public way. “The isolated Christian is an anomaly” (Howard Guiness, Total Christian War).
If a Christian were private only, he would be like a finger removed from the body, trying to exist by itself. It would have no source of food, sight, or smell. It could not continue to live. If it could live, it would be of no use to the rest of the body. So we say there is no such thing as a private Christian. All Christians are part of the Church, the body of Christ. “From him the whole body, joined and held together by every supporting ligament, grows and builds itself up in love, as each part does its work” (Eph. 4:16).
Christianity is personal and public. It is not possible to hide behind the words “personal and private” and still meet the minimum qualifications of a Christian given by Jesus.
That if you confess with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved. (Rom. 10:9-10)
I do not hide your righteousness in my heart; I speak of your faithfulness and salvation. I do not conceal your love and your truth from the great assembly. (Psalm 40:10)