In 1 John 3:11-24, the apostle emphasizes that the core message from the beginning of the Christian faith is to love one another, contrasting this with Cain's hatred and murder of his brother as an example of evil. True love is demonstrated not merely in words but in sacrificial actions, as exemplified by Jesus laying down His life for us, and we ought to help brothers and sisters in need. By loving in this way and keeping God's commands—to believe in Jesus Christ and love one another—we abide in Him, gain assurance before God, and know His presence through the Holy Spirit He has given us.