How do we know the doctrine of being poor in spirit is true?

The truth of being 'poor in spirit' is revealed through Jesus' teachings in the Beatitudes, particularly in Matthew 5. This doctrine emphasizes the necessity of recognizing our complete spiritual poverty before God. The Apostle Paul echoes this in Philippians 3, where he recounts his own spiritual transformation from self-righteousness to understanding his need for Christ. Therefore, it is supported by Scripture that recognizing our worthless state before God leads us to the grace found in Christ, making us heirs of the kingdom.