I was always taught that Satan meant "stumbling block" or some such. When Jesus cursed Peter saying, "Get behind me Satan" (Matthew 16:23), my parish priest, at least, always says Jesus is saying "don't try and trip me up, man."
A stumbling block and an accuser are certainly different things, both bothersome, but certainly different. Is Satan is used as some sort of homophone, meaning one thing in Job and Revelation and another in the Gospels?
Your parish priest has it right. The usage of the word "satan" (שטן) has evolved over time and several different usages were used concurrently. There is a good summary of the evolution of the usage on Bethelbooks.com.
With a bit of simplification we can say that there are three phases in the evolution of the usage:
In the pre-exilic portions of the OT, a "satan" is 1) a diversion , 2) an insurgency, 3) opponent. There is no personification and more importantly, no theological baggage attached.
In Zechariah 3:1 "the satan" appears for the first time. This is likely an obfuscated or coded reference to a particular person or party who opposed the high priest Joshua. It is probably not a reference to the later theological concept of "Satan" yet.
In later post-exilic portions of the OT, perhaps as a result of contact with Assyrian culture and Zoroastrianism, "the Satan" is personified, and identified as a spiritual entity, as in the prose prologue and epilogue of Job, Chapters 1,2 and 42:7-17, but still as an entity doing God's will.
In post-OT Jewish writings, in some of the Qumeran scrolls, in the NT and in the Gnostic gospels, "the satan becomes fully personified as "Satan" or the Devil, existing in the context of a developed angelology, and standing in opposition to God's will.
Despite this general development, the earlier, non-personalized and non-theological usage of a "satan" especially in the verb form "to satan" persisted in Jewish usage. I suspect that this is the sense that the word was used in Mat 16:23, and not the personified character of evil, Satan. Otherwise, how to explain the fact that Peter continued to be a valued disciple, and in Mat 17 is deemed worthy to witness a divine revelation (though he stays comically true to character when he volunteers to build earthly tabernacles for these heavenly characters).
For those of you interested in more detail here are the references:
Numbers 22:22 (NIV), "But God was very angry when he went, and the angel of the LORD stood in the road to oppose him. Balaam was riding on his donkey, and his two servants were with him." The Hebrew word here translated as "to oppose" is the infinitive verb form "l'satan' (לשטן). In my opinion, the correct meaning is "to divert" or "to intercept", from the root שות, similar to the usage translated as "go astray" in Number 5:12 (NIV) "Speak to the Israelites and say to them: 'If a man's wife goes astray and is unfaithful to him." and as in "turn aside" in Psalms 40:5 (NIV) "Blessed is the man who makes the LORD his trust, who does not look to the proud, to those who turn aside to false gods." In Numbers 22:22 it if God who sends a messenger to divert ("l'satan") Balaam. Same usage in Numbers 22:32. The Balaam story is built on three of similar verbs for "divert" that have one or more Hebrew letter in common, שטן, הטה, ירט.
I Samuel 29:4 (NIV) "But the Philistine commanders were angry with him and said, "Send the man back, that he may return to the place you assigned him. He must not go with us into battle, or he will turn against us during the fighting. How better could he regain his master's favour than by taking the heads of our own men?" Here the noun form "l'satan" is translated using an infinitive verb form "to turn against us".
II Samuel 19:23 (NIV) "David replied, 'What do you and I have in common, you sons of Zeruiah? This day you have become my adversaries! Should anyone be put to death in Israel today? Do I not know that today I am king over Israel?'". Here the singular noun form "l'satan" is translated as the plural "adversaries". In light of the previously mentioned usages and the usages in Kings, I think that a better translation would be "an interference to me", or "an insurgency". The word "adversaries" in modern English is too close to "enemies", which is not the case in this verse as the Zeruiah clan continued to be a necessary though problematic support of David's regime until the end. In any event, it might be that "This day you have become my adversaries!" should be interpreted as a rhetorical question in the Jewish form rather than an exclamatory statement of fact.
I Kings 5:4 (NIV) "But now the LORD my God has given me rest on every side, and there is no adversary or disaster." Here the noun "satan" is translated "adversary" and "pega ra" is translated as "disaster". There certainly were enemies all around, so I think that a better choice for "satan" here would be "no one to interfere" in the sense of an insurgency, and "pega ra" should be translated as "attacks". This better maintains the parallel construct of the verse. The meaning of the verse is not that there are no adversaries, but that Solomon has achieved a degree of deterrence so that the adversaries do not interfere with his kingdom nor do they conduct harassing attacks.
I Kings 11:14 (NIV) "Then the LORD raised up against Solomon an adversary, Hadad the Edomite, from the royal line of Edom." The noun "satan" translated as "adversary". Again, this is an insurgency, interference or a diversion, not an enemy (אויב).
I Kings 11:23 (NIV) "And God raised up against Solomon another adversary, Rezon son of Eliada, who had fled from his master, Hadadezer king of Zobah." Same a I Kings 11:14. Also I Kings 11:25.
I Chron 21:1 "Satan rose up against Israel and incited David to take a census of Israel." The support for a personified Satan rests primarily on the presumed historical context of Chronicles, as the Hebrew of this verse lacks the definite particle "the" (ה"א הידיעה) that we see in Zechariah 3:1. Note that Young's Literal Translation reads "And there standeth up an adversary against Israel, and persuadeth David to number Israel", i.e. no "Satan". In my opinion, based on the parallel verse II Samuel 24:1, the implied subject of I Chron 21:1 is God, who Himself stood as a "satan" or adversary against Israel by inciting David to conduct a census.
Finally, note that in Zechariah 3:1 (NIV) "Then he showed me Joshua the high priest standing before the angel of the LORD, and Satan standing at his right side to accuse him", the word "satan" is used twice, first as a noun with the definite particle "the", and as an infinitive verb translated as "to accuse". I think the meaning of the verb form here is to interfere with or divert, though possibly by means of false accusations. This is probably a reference to external enemies, the Samarian and Edomite parties that opposed the rebuilding of the Temple, and the reference to Joshua's coloured (not soiled) clothes in verse 4 is a reference to internal Jewish opposition from parties who did not accept the purity of Joshua's priestly lineage, as the wearing of coloured clothes by priests was used to signal doubtful lineage.
Satan (שָׂטָן) in Hebrew means “enemy” or “adversary” but this “opposition” is in the Old Testament directed in the specific sense of an “accuser”. The idea seems to be that since man has fallen into sin under the curse of Law, the Devil appeals to God’s own justice in order to accuse men and keep them under his domain of death. He is a kind of 'receiver of souls' that are 'obnoxious under law' and 'resigned to death'. For example, when God was about to restore the exiled church back into Jerusalem, Joshua (meaning savior) the high priest was a symbol of the ministry of the church promised to be restored from exile. However, Satan opposes this restoration of this ministry through 'accusation'. Possibly because of the sins of the Joshua, the priests and the people, Satan accuses Joshua as their representative, demanding they remain dead under the broken Law. The Lord intervenes and rebukes Satan in his accusations against God’s people.
Then he showed me Joshua the high priest standing before the angel of the LORD, and Satan standing at his right side to accuse him. The LORD said to Satan, "The LORD rebuke you, Satan! The LORD, who has chosen Jerusalem, rebuke you! Is not this man a burning stick snatched from the fire?" (NIV Zechariah 3:2)
This is the same way in the case of Job, which was mentioned in the question. In Job 2:3-5 Satan 'accuses Job' saying that he was not a good man as God had said, but that if God would remove his protection he would be as wicked as the rest and ‘curse God’s face’.
In the New Testament Satan (Σατανᾶ) carries the same meaning. In the New Testament we see this opposition is even more clearly defined by his role of 'accuser'. For example, the Devil wants to ‘sift’ Peter just like he did Job:
"Simon, Simon, Satan has asked to sift you as wheat. But I have prayed for you, Simon, that your faith may not fail. And when you have turned back, strengthen your brothers." (NIV Luke 22:31-32)
This is very similar to Job’s situation but the Lord rebuking Satan is replaced by our Lord’s intercessory prayer, clarifying the roles in a clearer light than found in the Old Testament but without deviating from the original concept.
In the case where the Devil opposes Christ directly he can’t be properly accused, as he is sinless, yet the opposition is like an accusation. According to the flesh Christ’s willingness to die was not right and so Peter’s in his rebuke of Jesus is still an accusation, only according to the flesh. However, is not that the same case with all the Devil’s accusations? Though we be guilty, yet when accused by Him, it is a lie!, for in Christ we are righteous. This is why Revelations has the bottom of the matter spelled out:
Then I heard a loud voice in heaven say: "Now have come the salvation and the power and the kingdom of our God, and the authority of his Christ. For the accuser of our brothers, who accuses them before our God day and night, has been hurled down. They overcame him by the blood of the Lamb and by the word of their testimony; they did not love their lives so much as to shrink from death. (NIV Revelation 12:11)
Therefore, Satan is a stumbling block and opponent in his accusations and these two aspects of his person are complimentary, not divergent.
Wikipedia is helpful here; much of this answer is adapted from there.
The Hebrew satan [שטן] means to oppose or obstruct, more actively than to simply be a stumbling block.
In Job and Zechariah, though, mention is made of a particular celestial being identified as ha-satan [השטן] with the definite article ha-; so, “the satan” or “the adversary”. This angel’s job (i.e., whom is he opposing?) can be understood variously in Job, but in Zechariah he’s pretty explicitly opposing Joshua the high priest (until God tells him to stop).
In the context of Matthew, “Get behind me, Satan” wouldn’t mean “don’t try and trip me up, man” so much as “don’t get in the way, man”.
(I wonder whether the pun on Peter’s name with “rock” is relevant here.)
Satan as accuser comes from Jewish midrashic tradition, which ascribed to this angel three related roles: (1) he tempts man to do evil, (2) reports on this evil to God, then (3) executes God’s punishment on the man. It is in this second role that he is called the “devil” (from the Greek diabolos [διάβολος], meaning slanderer). This idea would be current during the 1st century CE, and would explain the conflation of the satan’s rôles in the Christian NT. But I don’t think it’s directly relevant to the verse in Matthew.
