If you ask most believers to explain what fallen angels are and how they came to be "fallen" they will explain the rebellion of Satan and those who followed him which took place before man was made. Few believers will mention a second group of rebels which, nonetheless, have gotten plenty of attention in scripture. The reason that this is such a little known event in spite of its biblical references, is that the book which gives the full account of it has been stricken from the canon. Imagine if we lacked the book of Exodus and still were left with the many references to the events of Exodus throughout the rest of scripture. Would readers be able to understand the full story of how Hebrews were kept as Egyptian slaves, when this happened and how they were liberated, not to mention the 40 years of wandering in the desert and receiving the law? How might understanding His law change if there was no full record of how it was received?
The book of Jude is accepted as valid scripture by canon and most believers but it has some things to say that lead to vast amounts of speculation by themselves. Take a look at these verses:
" Now Chanowk (Enoch), the seventh from 'Adam, prophesied about these men also saying, "Behold! The Master comes with ten thousands of His saints to execute judgment on all, to convict all who are wicked among them of all their wicked deeds that they have committed in a wicked way, and of all the harsh things that irreverent sinners have spoken against Him." " Jude 14,15
Jude states he is quoting the words of Enoch, the seventh from Adam. It goes without saying that there is a huge gap of time between the lifetimes of Enoch and Jude, so how did Jude come by a prophecy from this ancient forefather of his unless it was written down and well known? Does it make any sense to assume his contemporary audience would be scratching their heads in confusion, wondering where Jude came by this unknown prophecy allegedly given by Enoch, or does it make sense that Jude's audience was already familiar with this prophecy and would understand from where he got it?
compare the above verses in Jude to these verses from the book known as 1 Enoch or the "Ethiopian Enoch" :
"And behold! He cometh with ten thousands of His holy ones To execute judgement upon all, And to destroy all the ungodly: And to convict all flesh Of all the works of their ungodliness which they have ungodly committed,And of all the hard things which ungodly sinners have spoken against Him." 1 Enoch 1:9
I think it could not be any clearer that these were the very words Jude repeated in his writings as he himself and his contemporaries had access to and knew well, the contents of 1 Enoch. Amazingly i have actually had certain believers argue that "it's not an exact quote." Even with not taking into account having been translated from two different languages by separate English speaking individuals, the similarity of these two verses would constitute some incredibly improbable coincidence on multiple levels.
this might be the most well known Jude-1 Enoch connection but it's not the only one. Here is another:
"And the angels who did not keep their proper domain but left their own abode He has reserved in eternal chains under darkness for the judgment of the great day" Jude 6
It seems to be that for the most part believers take for granted that this is simply speaking about Satan and his followers, the problem with that idea comes from the fact that we all well know how active and present Satan's influence in the world has been since the fall of man. He's hasn't been bound in chains nor have his minions been. Some like to take this verse to mean figurative chains...meaning that Satan and his cohorts are "spiritually" under bondage...very interesting irony if you think about it carefully...Satan and his minions Are spirits, as the nature of angels are, so to bind one spiritually is not very figurative at all. 1 Enoch describes a certain group of angels, however, who were literally bound in fetters and contained in prison cells under the earth for sins which were different from those of the first rebellion by Satan and his followers:
"And the Lord said unto Michael: 'Go, bind Semjaza and his associates who have united themselves with women so as to have defiled themselves 12 with them in all their uncleanness. And when their sons have slain one another, and they have seen the destruction of their beloved ones, bind them fast for seventy generations in the valleys of the earth, till the day of their judgment and of their consummation, till the judgment that is 13 for ever and ever is consummated." 1 Enoch 9:11,12
Immediately following verse 6 in Jude which deals with the angels who were bound in chains, a comparison is made between this subject and the sins of Sodom and Gomorrah.
"as Sedom and Amorah and the cities around them in a similar manner to these, having given themselves over to sexual immorality and gone after strange flesh, are set forth as an example suffering the vengeance of eternal fire" Jude 7
...and by referring back to 9:11&12 in 1 Enoch it's clear why such a comparison is made. "'Go, bind Semjaza and his associates who have united themselves with women so as to have defiled themselves"
The sin for which these angels were bound was sexual immorality. They took wives from among humans and had children by them. This is both a violation of His law against unlike kinds procreating and a violation of the nature of angelic beings, as no female angels were formed and they were not made to procreate.
Jude is, by far, not the only place references to the events described in 1 Enoch can be found. Some are more clear and some less due to a pointed attempt to translate out some of the implications of connectedness to this book. One pretty clear reference can be found in Genesis 6.
"Now it came to pass when men began to multiply on the face of the earth and daughters were born to them
that the sons of the 'Elohiym saw the daughters of men were beautiful and they took wives for themselves of all whom they chose. " Genesis 6:1,2
"There were nephilim on the earth in those days, and also afterward, when the sons of the 'Elohiym came in to the daughters of men and they bore to them. Those were the mighty men who were of old, men of renown" Genesis 6:4
The word "nephilim" often rendered "giants" does not actually mean giant..though the connection between nephilim and giant stature is recorded elsewhere, particularly in Numbers. Nephilim is sometimes translated as "fallen" though it is perhaps better translated as "a feller" in the sense of something or someone who strikes down others in violence. Interestingly, it is also connected with a pre-mature or miscarried baby.
The term "sons of the Elohim" or "sons of God" is understood by many believers to refer to men who are faithful followers of YHWH. This is not at all the meaning of this phrase. The phrase has nothing technically to do with morality, but rather of origin. A being who has no father other than their Creator is a Son of Elohim. Adam is called a son of Elohim because he was directly created by Him, angels are sons of Elohim because they were directly created by Him, Yahushua is called The Son of Elohim, having no mortal father and being unique in that He is the only Begotten (born of flesh by the Will of the Holy Spirit) son of Elohim. Yahushua gives men the Power to become sons of Elohim in that they forsake their sinful flesh birthright to be born again as children of YHWH. This last is not the natural state of man, but rather the privilege of believers to become a New Creature in Him. The old Testament does not refer to men as presently being sons of Elohim, no matter how faithful they are.
For a very long time Christians have had an idea drilled into their minds which makes very little sense rationally. The idea that the canon is flawless. Christians will often parrot exactly what they have heard their seminary trained leaders tell them " There can't be mistakes in it, He promised to preserve His Word"...and He did. He did not, however, say that men would not be able to add or subtract information, translate it badly or otherwise attempt to subvert its messages. This is why believers can not take a lazy approach to learning His word....It Is out there...but it is up to you to crack open a Strong's concordance..study and test in His Spirit extra-canonical texts and research carefully, thoroughly and without prejudice where various translations of the bible come from and who was behind them. Neither can people accept, without question, some single English translation of canon nor can they throw up their hands and determine there is no way to know His full message..neither are realistic. There is no doubt He has preserved His word on Earth...now it's His people's job to Seek it.