Clearly, Peter is borrowing these words from Jesus’ declaration of blessedness in Matthew 5:11. The term “blessed” (also used in 1 Peter 3:14) refers to being happy, joyful. To our minds, suffering for the gospel excludes the possibility of happiness. Jesus, however, had declared such a person “blessed” (happy), and Peter simply echoes Jesus’ promise. In fact, he himself experienced this joy (Acts 5:41).
14 If you are insulted for the name of Christ, you are blessed, because the Spirit of glory and of God rests upon you.