For if God did not spare angels when they sinned, but cast them into hell and committed them to pits of darkness, reserved for judgment;2 Peter 2:4(NASB)
The focal subject throughout this second chapter of Peter, is false teaching. There always has been and always will be false teaching. There will always be error and deception, side by side with the truth of God's Word. Holy men of Israel spoke the Word of God in spirit and in truth, but alongside them were those that were teaching falsehood, delusion, and deceit.
Both in the Old and New Testaments, we discover ungodly lies and satanic trickery, and here, in the first three verses of 2nd Peter, we are given a description of these sins. Peter lists three examples of God's judgement against this deceptive trickery, including the judgement of angels, judgement of the old, pre-flood world, and the judgement of the cities of Sodom and Gomorrah.
God judges sinfulness in every realm of His creation, and we discover that He has even judged the angels who sinned alongside Satan. These fallen angels left their first estate, for we read, "God did not spare the angels when they sinned, but cast them into a place called Tartarus, and committed them to pits of darkness, reserved for judgment."
All sin must be judged, and a full payment for sin must be made - which God has determined is the sacrificial death of an innocent victim. The only substitutional sacrifice that was acceptable to God for a man's sin was the death of a close kinsman of the sinner, who must be willing to give his own life to save another. JESUS is that Kinsman-Redeemer who gave His life for us. Jesus is the only acceptable sacrifice for the sin of the world.
The sacrificial offering for the sin of mankind was made by Christ - the Innocent for the guilty. Our sin was judged at the Cross, and payment was made through the shed blood of a perfect man - the Man, Christ-Jesus. Fallen members of the human race are redeemed by faith in Christ's sacrificial death. Those who believe are born of the Spirit of God, and have had their sins already judged and paid for - in Him.
The price of sin was paid for at the Cross. Propitiation for our sins was made through Christ, such that all who believe on Him are forgiven of their sin and declared righteous by God. However, Scripture is very clear that Christ died for the sin of fallen human-kind and not for the sin of fallen angelic beings. The angels that sinned against God have no offer of salvation but have been cast into hell and committed to pits of darkness, where they wait for judgement.
Man was made in the image of God, not angels. The only begotten Son of the Father became a man, not an angel. Christ was made in the likeness of human flesh (not angel-flesh). Jesus was born into the human race - not the angelic host. Christ became a member of humanity.. to save MAN from sin, which is why He was called the Son of Man. He was identified with the sin of sinful man and not with the sin of fallen angels, who must suffer the consequences for their own sin - and the almighty God has already purposed an irrevocable judgement upon those angels that left their first estate.
Today these fallen angels are imprisoned in Tartarus until that final judgement day - when they, together with Satan, unsaved humanity, and hell itself, will be cast into the Lake of Fire, which burns with unquenchable fire. This Lake of Fire was originally prepared by God for the devil and his angels, who left their first estate and sinned against the Lord of heaven and earth.
Some liberal teachers like to consider this description of the imprisoned angels to be metaphorical. But there is no indication that this is not a literal place of confinement for this group of sinful angelic beings. It appears that these fallen angels are condemned criminals, who are shackled with the strongest chains in a dungeon of pitch blackness. We are told that they are contained in a section of hell called Tartarus - which means place of punishment.
Though the angelic host were collectively created in a holy state, placed in a perfect environment, and living in the presence of God, they were not immutable.. and like human-kind, the angelic host were given a free-will. Like humanity, they were afforded the freedom to choose between doing good and doing evil. However, they were not furnished with the opportunity to be redeemed of their sin. They fell according to their own volition.. but they were not tempted to sin. Unlike man, angels were not tempted to sin by another species of God's creation - they were tempted by Satan - one of their own angelic kind.
God purposed in His heart to redeem fallen man, who was tempted to sin by Satan - a fallen angelic being. This prideful cherubim, who determined to ascend to heaven to raise his throne above the stars of God.. to ascend above the starry heights of the clouds and to make himself like the Most High, drew with himself, a third of God's holy angels who joined him in his ungodly rebellion, and have been judged for their sin, "for God did not spare angels when they sinned, but cast them into hell and has committed them to pits of darkness, reserved for judgment."
Adam's sin was imputed to all men, but God in His grace determined that by the sacrificial death of one MAN - the man Christ Jesus, ALL mankind, not angel-kind, would be given the opportunity to be saved by grace through faith in God's own anointed Messiah, Jesus Christ, Whom He would send.
The choice for every man is to believe and be saved, or not believe and be condemned, and one's eternal destiny rests on the choice that each man makes.
Heavenly Father, I praise and thank You for purposing that You would redeem mankind from their sin. Thank You for sending Jesus Christ as the Son of Man, to pay the price for my transgressions. Thank You that my sin has been judged at the Cross, and that I have been declared righteous in Your sight, by faith. Father, the terrible judgement of the angels that left their first estate, and joined in a heavenly rebellion against Your holy name, is a sombre reminder of the destructive nature of sin. Thank You that by Your grace, You purposed to redeem mankind, and to adopt all who trust in Your only begotten Son, into Your own immortal family. Keep me from minimising the destructive element of sin and its shocking, and eternal consequences, and use me to share the truth of the gospel of grace, with men and women who are dead in their sins and bound for the lake of fire - unless they believe on the Lord Jesus Christ for their salvation and forgiveness of their sin. This I ask in Jesus' name, AMEN.