Revelation 2:11

11. Not be hurt of… second death However he may suffer the death of martyrdom, his crown of life exalted him far above the second death. The promise corresponds, also, with the self announcement in Revelation 2:8. The second death, in Revelation 20:15, is defined as the being cast into the “lake of fire.” Neither term second death nor lake of fire is used in any scripture outside the Apocalypse. Gehenna, a figure drawn from the valley of Hinnom at Jerusalem, used by our Lord, and used in the New Testament twelve times, comes most nearly to the same conception. Both Gehenna and second death are terms introduced into Jewish biblicism by the Targumists, the Hebrew paraphrastic translators of the Old Testament.

How the term second death was understood at Smyrna may be inferred from certain passages from the above quoted letter from the Smyrnean Church. Thus, when the proconsul threatened Polycarp with death by fire, the latter replied, “Thou threatenest me with the fire that burns for an hour and in a little time is extinguished; for thou knowest not the fire of the future judgment, and of the eternal punishment that is reserved for the ungodly.” Of the other martyrs the Church says, “Even the fire of their persecutors seemed cold unto them, for they had before their eyes the prospect of escaping that which is eternal and unquenchable.”