3:14 happy are ye. Here Peter echoes one of the Lord’s beatitudes in the sermon on the mount (Matthew 5:10; see also I Peter 4:12-14).
3:14 terror. See Isaiah 8:12-13, which Peter here quotes and applies. In context, Isaiah was encouraging the Jews in light of an impending invasion by the Assyrian armies, along with a hostile confederacy uniting Syria and the northern kingdom of Israel against Judah. Peter appropriated God’s promise as applying also to the Christians of any period who might be facing persecution.