Why is it terrifying to think one could believe in vain?

The idea that one may believe in vain is alarming, as it signifies that decades of devotion, service, and faith could be unrecognized by God. The biblical warning serves as a profound source of introspection, impacting genuine believers more significantly than those who are unrepentant. It reflects the fear of standing before God and realizing all past faith and deeds were insufficient, a fear echoed in Matthew 7:22-23, where some professing believers are turned away from His presence despite their activities done in His name. This highlights the necessity of true faith that rests upon Christ alone for salvation.