Ancient historical records prove beyond a doubt that the early Christians included Enoch in the Bible. 

Tertullian was a high ranking church official in the late 100's and early 200's AD.  Tertullian wrote,

"Enoch had come before… but why restate any more Scriptures as if the Holy Spirit’s word were not enough?"[1] 

Here, we can plainly see that Tertullian explicitly calls Enoch "Scripture."  He was not the only one.

     In the early 200's AD, a professor of Christian studies named Origen wrote, "Perhaps someone will ask us if we can find a Scripture that supports our opinion on the subject… in Psalms, the prophet says… and also Enoch, who said in his book…"[2]  Origen explicitly called Enoch scripture, on par with the Biblical book of Psalms, and used its authority to prove an unrelated point.  This is de facto canonization of the book.

     In fact, all ancient Christian sources within 200 years of Jesus' life on earth, and who happened to mention Enoch, either expressly endorsed Enoch as scripture, or they allude to it as a source of truth.  Not until the middle of the 3^rd century did anyone question the book of Enoch.

     About 155 AD, the early Christian apologist Justin Martyr said,

The angels disrespected their lofty position.  They became infatuated with women, and so they had children who became those entities known as demons.  Moreover, after they did that, they lorded it over humanity by means of occult literature, fear, retributions, and also by teaching the offering of sacrifices… because the demons needed such things.[3]

From this, we may conclude that Justin Martyr had read and accepted Enoch, for Enoch tells the exact same story.  There is no other place Justin Martyr could have received this information – in particular, that the angels taught the women occult magic, that their children oppressed humanity, and that their children became incorporeal spirits, i.e. demons, after death – this information is only contained in Enoch, which corroborates Justin Martyr as follows:

The children of heaven, the angels, saw the women and wanted them, and said to each other, "Let’s take the humans’ daughters for our wives and have children…" And they taught them sorcery, chanting, divination, and making potions; then the women conceived and gave birth to large giants...  The giants ate the people's food until the people grew tired of feeding them… and they accused them for being tyrants.[4] 

The giants who are born from both spirit and flesh will be the evil spirits of the earth.  Evil spirits escaped their bodies.  From the first, when the holy ones fathered them, they became watchers… The spirits who dwell in heaven belong to heaven, but the spirits who were born on the earth belong to the earth, and they must dwell there.  The spirits of these giants… will bring distress.  They won’t eat or drink anything, nor are they visible.[5]

Hence, they are demons.

     The traditions of Enoch permeate early Christian literature.  Below are some more examples.  Irenaeus, the Catholic bishop of Lyons, claimed angelic sexuality and the resulting violent offspring were the reason for Noah's Flood:

In Noah’s day, [God] justly brought on the Flood so that a most notorious breed of people might be destroyed.  These people were incapable of doing anything good for God, because the sinful angels had commingled with them. God did this to bring an end to these people’s transgressions, but still preserve a proto-type of Adam.[6] 

Contemporary with Irenaeus, about 175 AD, the philosopher Christian Athenagoras wrote,

Just as men have free moral agency… so do the angels… but some of them grieved their original nature… and they succumbed to lust for virgins.  They were conquered by the flesh, and they abused the authority that had been granted to them.  Becoming evil and negligent, they were sex partners with virgins.  Thus, they fathered those known as giants.[7]

About 190 AD, the prolific early Christian author Clement of Alexandria wrote,

For example, the angels who renounced the beauty of God for a beauty that fades…[8]

Commodianus, a late 3^rd century Christian from Palestine likewise left a record saying,

When [angels] were sent down, they hated [God’s] laws.  The loveliness of women distracted them.  Then they could not return to heaven, since they were now unclean.  Being rebels from God, they blasphemed Him.  Then the Highest declared His judgment against them.  Giants are said to have been born from them.  They taught the earth skills, such as the dyeing of wool, and all other things that are done.  When they died, humans built idols to them.  But they were the offspring of evil, so the Almighty did not allow for them to come back to life once they were dead.  So now they wander around and possess various bodies, and these are the gods that you (pagans) worship and pray to.[9]

Another early Christian named Cassiodorus wrote,

But the angels… since they vowed to lust, cannot be redeemed… Enoch, the seventh from Adam, as Jude says, also prophesied about these…[10] 

Lactantius, another early Christian leader, wrote,

The deceitful ruler of the earth used his association with them to gradually entice (the angels) to commit crimes, and to pollute themselves by having sex with women… Those who were born from these were not admitted into the underworld, just as their fathers were not admitted into heaven, for they were a mixture of angel and human.  So there came to be two types of demons – one from heaven and the other from earth.[11]

          It is impossible for modern-day Christians to truly emulate the most ancient and purely genuine apostolic church without understanding and accepting the book of Enoch, for that book's traditions were the basis for very central and unquestioned doctrines of the early Christians.