The blessing that a Christian is to give to the reviler includes finding ways to serve him, praying for his salvation or spiritual progress, expressing thankfulness for him, speaking well of him, and desiring his well-being. A person whom God has given undeserved blessings instead of judgement, should seek the blessing he will receive when giving a free gift of forgiveness to someone who has wronged him.
Commentary from the MacArthur study Bible, notes for 1 Peter 3:9.
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