"'You shall not take vengeance, nor bear any grudge against the sons of your people, but you shall love your neighbor as yourself; I am the LORD." -- Leviticus 19:18
Civilized society is an ordered society. The world secures order by laws. God's kingdom is ordered by love.
Worldly society exists to secure a just order. Individuals are not permitted to execute vengeance on their own. Justice is secured by the rule of law.
God's kingdom secures abundant and eternal life. Individuals are not permitted to hold grudges. Fellowship is secured by the rule of love.
The law preserves order by fear and force. Love secures order by grace and forgiveness. The law is restrictive. Love is liberating.
Loving your neighbor as yourself fulfills the law and creates a fellowship of happiness and hope.