What does it mean that God has mercy on whom He will?

The phrase that God has mercy on whom He wills underscores His sovereign authority in the dispensation of grace. This means that salvation and mercy are determined not by our actions or qualifications but by God's will alone. Romans 9 states that God has the right to choose vessels of mercy and vessels of wrath, illustrating the depth of His sovereignty in salvation. This doctrine of mercy emphasizes that our hope is not found in our performance but in the unmerited favor of God, leading to a profound sense of gratitude and assurance for believers.