An angel as a primeval enemy of humanity
The Hebrew noun satan, along with related nouns and verbs, are semi-common in the Hebrew scriptures. These terms are used in a variety of contexts and refer to a variety of individuals.
In Numbers 22.22,32, for example, it is an angel explicitly acting on God's behalf who is identified as a satan, meaning 'adversary'. In 1 Samuel 29.4, it is David who is identified with the word. In other passages the 'satan' is a human acting as an opponent (2 Samuel 19.22; First Kings 5.4; 11.14,23,25). In yet another, the term satan describes an accuser in a court setting, who stands to the right of the person being accused (Psalm 109.6).
During the Second Temple period (538 BC and after) we see a development in Jewish theology concerning angels. Several books begin giving names to angels, elaborating on their roles in their service before God (e.g. Raphael in the book of Tobit; Gabriel and Michael in the book of Daniel; many more in 1 Enoch). This included an expanded understanding of a specific angel who acts as an 'accuser' (satan) in the heavenly court setting.
Zechariah 3, written c.520 BC, describes the satan as standing to the right of the high priest Joshua in order to accuse him, just like we find in the court setting of Psalm 109.6. It is worth noting that in both passages, it is implied that the satan is doing wrong: Psalm 109.6 makes the satan parallel to 'a wicked man', and in Zechariah 3 the satan is 'rebuked' for his accusation against Joshua.
The book of Job, which is generally dated to the 6th-4th centuries BC (contemporary to or later than Zechariah 3) has the satan again appearing in the heavenly court. Here he is not explicitly 'evil', but he is associated with tempting humans to sin, and he inflicts trouble and pain.
In 1 Chronicles 21.1, written about the middle of the 4th century BC, the editor has changed 2 Samuel 24.1, so that instead of God himself inciting David to sin, it is satan who has done it (probably, like in Job, at the instruction of God). The lack of a definite article in Hebrew is often cited as evidence that 'satan' has transitioned from a descriptive label into a proper name, but this claim is not necessary; earlier uses of the word lack the definite article as well when 'satan' is clearly not intended as a proper name (1 Kings 5.4 and 11.14,23,25 all lack the definite article).
But it is after this time that angelology truly starts to focus on enemy angels. These include:
- 1 Enoch (several elaborate descriptions of sinful angels, including brief references to the satan)
- Jubilees 17.16 (describes 'the prince Mastema', apparently an angel, interacting with God in a manner identical to the satan of Job 1-2), c.150 BC,
- the Synoptic Gospel books (the satan / the devil / Beelzebul), e.g. Mark 3.23-27 (and parallels), Matthew 4.8-9 (and parallel), Matthew 25.41, Luke 10.18 (and parallel), from the mid- to late-first century AD,
- Hebrews 2.14 (the devil), mid- to late-first century AD,
- 1 John 3.3 (the devil), late-first century AD,
- the Gospel of John (the satan), e.g. John 8.44, late-first century AD,
- Jude 9 (possibly quoting an older Jewish work, effectively equates 'the devil' with the satan of Zechariah 3), late-first century AD
- Martyrdom of Isaiah 2.2 (the satan), late-first century AD
The serpent
Even before the Revelation was written, different Jewish authors from a variety of traditions were associating the satan with the serpent.
Second Enoch 31.1-5, a Jewish apocalypse from the late first century AD (thus contemporary to the Revelation), explicitly identifies the satan with the serpent. God, speaking in the first person, says:
Adam has life on earth, and I created a garden in Eden in the east, that he should observe the testament and keep the command. I made the heavens open to him, that he should see the angels singing the song of victory, and the gloomless light. And he was continuously in paradise, and the devil understood that I wanted to create another world, because Adam was lord on earth, to rule and control it. The devil is the evil spirit of the lower places, as a fugitive he made Sotona from the heavens as his name was Satanail, thus he became different from the angels, but his nature did not change his intelligence as far as his understanding of righteous and sinful things. And he understood his condemnation and the sin which he had sinned before, therefore he conceived thought against Adam, in such form he entered and seduced Eva, but did not touch Adam. (R.H. Charles translation)
Life of Adam and Eve identifies 'the devil' as the one who deceived Eve, whether by speaking to her directly, or by using the serpent as a mouthpiece.
First Timothy 2.9-15, during instructions of how women should dress and behave, mentions Adam, Eve, and women being deceived. When the author later gives additional instructions to women in 5.9-16, he again closes the section by mentioning women being led astray, this time mentioning 'the adversary' and 'the satan'. The parallelism between the two passages implicates the satan in the deception of Eve in Genesis 3.1-6,13.
Romans 16.20 says:
The God of peace will soon crush Satan under your feet. (ESV)
The context is specifically about deception (Romans 16.17-19), so conceptually we are in the same realm as Genesis 3.15: a deceiver being crushed under foot. So while the Greek text of Romans 16.20 does not use the same verbs or nouns found in the Septuagint version of Genesis 3.15, it is still possible this was the intended background to what Paul wrote.
1 Enoch 69.6 says:
And the name of the third [leader of the angels who left heaven] is Gadre'el. This is the one who showed all the blows of death to the sons of men, and he led Eve astray... (Nickelsburg & VanderKam translation)
In this case it is not 'the satan' who is identified as the deceiver of Eve, but it is certainly an angelic figure who sinned in the ancient past (the context is an elaboration of Genesis 6.1-4). It should be noted the book of 1 Enoch is not consistent in its portrayal of angels; it is a compilation of several separate Enochic texts, all of which have undergone some degree of editing. Another part of the book refers to the wicked becoming 'servants of Satan'.
Wisdom 2.21-24, written in the second or first century BC, states:
Thus they [the wicked] reasoned, but they were led astray, for their wickedness blinded them, and they did not know the secret purposes of God, nor hoped for the wages of holiness, nor discerned the prize for blameless souls; for God created us for incorruption, and made us in the image of his own eternity, but through the devil's envy death entered the world, and those who belong to his company experience it. (NRSV)
No explicit mention is made of the serpent, but the author certainly has the early chapters of Genesis in mind. Immediately before saying 'through the devil's envy death entered the world', the author mentions that humans are made 'in the image' of God, a concept found in Genesis 1.26-27, 5.3, and 9.6.
Conclusion
Given the above, the Revelation is entirely in line with existing Jewish thought when the author (a) identifies the satan as the primeval enemy of God and humanity, and (b) identifies the satan as the serpent in the garden of Eden.