What is the most widespread error in the church? There are oh, so many, of course: We have professing believers who say they love Jesus but hate the church, his bride. We have apparent Christians who call the work of Christ divine child abuse. We have church-going men and women who believe it doesn’t matter with whom they sleep, what media they consume, or where they go (and heaven help anyone who says otherwise).
These are all pretty serious things, to be sure. But they’re not the most consistently widespread problem. If anything, these are symptoms of the larger error. That error? The rejection of the Old Testament. Writing a century ago, in a time in church history very similar to our own, Herman Bavinck put it this way:
The worst and most widespread error is the rejection or neglect of the Old Testament. Marcionism repeatedly reemerged in the Christian church and plays a large role in modern theology as well. All this arbitrary use of Holy Scripture leads to one-sidedness and error in theology and to pathology in the religious life. In that setting the full and rich configuration of truth does not come to light. Either the person and work of the Father or of the Son or of the Holy Spirit is then sold short. Injustice is done to Christ either in his prophetic, or his priestly, or his royal office. The Christian religion loses its catholicity. The Christian head, heart, and hand are not harmoniously molded and guided by the truth. Only the whole Bible in its fullness preserves us from all these one-sidednesses. (Reformed Dogmatics vol. 1, 617)
I have never met a spiritually healthy, well-balanced Christian who neglects the Old Testament. Chances are, neither have you.
If we ignore the Old Testament, and the rich promise of Christ contained within it, we do so at our spiritual peril. If we teach that it’s no longer necessary, we ought to have millstones tied around our necks. If you overlook it, you impede your ability to respond to objections to it from non-Christians.
In other words, if you want to lose your heart, lose your hands or lose your mind, just ditch the Old Testament.