“For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;”
King James Version (KJV)
2:4 Cast them down to hell - The bottomless pit, a place of unknown misery. Delivered them - Like condemned criminals to safe custody, as if bound with the strongest chains in a dungeon of darkness, to be reserved unto the judgment of the great day. Though still those chains do not hinder their often walking up and down seeking whom they may devour.
2Pe 2:4 For if God spared not the angels that sinned. In order to show that judgments on these wicked teachers are sure, Peter cites examples. Even angels when they sinned were subjected to punishment. But cast [them] down to hell. The sinning angels were cast out of heaven. The word rendered "hell" is not Gehenna, but Tartarus, a Greek term used for the place of future punishment. Delivered [them] into chains of darkness. "Pits of darkness" (Revised Version); possibly dungeons of darkness gives the idea. Compare Jude 1:6 Both passages point to a time when angels sinned, fell, and thus became angels of darkness.