Why is Christ the only needful thing?

Christ is the only essential aspect of life for believers because He embodies the fulfillment of all that God requires for salvation. Ecclesiastes 12:13-14 summarizes that fearing God and keeping His commandments is the whole duty of man, which can only be accomplished in Christ, who perfectly kept the law. Everything else in life is ultimately vain and will not last, while knowing and having a relationship with Christ provides eternal life (1 John 5:12). This prioritization of Christ underscores the teaching that all human pursuits are fruitless without Him, reinforcing His place as the one thing needful in the life of every believer.