How do we know the effectiveness of God's grace?

The effectiveness of God's grace can be seen in how it operates in the lives of believers. As shown in the story of David and Goliath, David trusts not in Saul’s armor but in the God who has proven Himself through past victories. Paul encourages believers by stating that God’s grace is sufficient, implying that through trials and tribulations, God's grace manifests powerfully, confirming its effectiveness. Furthermore, through testimonies of personal transformation and deliverance from sin, we see God's grace at work, proving that it reaches deeper than our sin and shortcomings.