(2 Timothy 3:16) The Bible is inspired by the Holy Spirit
Over the decades I have been a Christian leader, I have watched individuals and churches fall away from following Jesus Christ.
The primary reason they began wandering from God is they started to downplay the importance of the Bible as the objective word of God. They began to question rather there is any real eternal truth at all. They began to consider the ethical teaching of the Bible as out-of-date for the modern world.
2 Timothy 3:16 tells us that the Bible is inspired, literally God-breathed. Another word for breathed is wind, which is the Holy Spirit.
Once an individual or church begins to reject the truths of the Bible as being fully trustworthy, their spiritual decline begins. I have seen it many, many times.
If the Bible is not at the center of our Christian lives, then our Christian faith will be weak, if not absent. The Bible is not magic, it is God-inspired and useful for teaching, rebuking, correcting, and for training in righteousness.
In order to grow and mature as a Christian, reading/listening and meditating on the Bible is a central requirement. When we absorb and apply the truths of the Bible to our lives, we develop a biblical worldview, a way of seeing the world through the truth of God. We read the Bible to renew our minds; reading the Bible is not simply a religious virtue.
This is an absolute fact: If we neglect biblical truth, we will spiritually decline. If we prioritize biblical truth, we will spiritually grow. Today, there are numerous ways to hear and absorb biblical truth, from podcasts, online sermons, and even daily devotions you can receive by email, like this one.
There is no true Christian that is not a biblical Christian.