TWH: Forms of the Hebrew word שָׂטָן (śayṭan) can be found really throughout the Old Testament. Antonio pointed out a couple of its uses in his post (Part 2), e.g., Num. 22:22a and 2 Sam. 19:22a. It generally has a negative overtone, although the very nature of the word does not actually say anything about whether a person is actually evil. Someone who was "evil," for example, could use this word to describe someone that was "good." We can't determine based on a lexeme whether or not someone or something is by nature evil.
One reference also worth pointing out is 1 Chron. 21:1, where a being named Satan "stood up against Israel and moved David to number the descendants of Israel." Who is this one that took a stand "against Israel" and brought the census about in the days of David? This is a rather peculiar verse, especially when we see what it says in 2 Sam. 24:1: "Now again the anger of the LORD burned against Israel, and it incited David against them to say, 'Go, number Israel and Judah.'" Who was the one responsible for David conducting a census? Was it this one named "Satan" or was it the "anger of the LORD?" Writing about these verses, Steven S. Tuell says the following:
"Christians will be quick–indeed perhaps too quick–to identify David's tempter with the personal devil and spiritual adversary of the New Testament, where the personal name Satan is used thirty-five times. In the Hebrew Bible, however, this term often appears with reference to a human enemy . . . . Here, instead of the śayṭan, the text reads simply śayṭan. Most interpreters take this to mean that Satan here is a proper name–the first such occurrence in Scripture, and the only one in the Hebrew Bible. However, it is also possible to translate the term as "an adversary" (Japhet 1993, 374-375). In that case, some nameless, human advisor would be responsible for influencing David's decision. Favoring this mundane reading is the absence of any other trace of a personal Satan in Chronicles." (First and Second Chronicles, 86).Tuell goes on to point out that the Septuagint translator recognized this as a spiritual adversary and used the Greek word διάβολος in place of the Hebrew. The Greek could be used to refer to a human adversary, but such uses as Tuell points out are rare; only three such uses are found, and they are in Psalms (109:6), Esther (7:1; 8:1), and 1 Maccabees (1:36).
What we find in 1 Chronicles is, in my opinion, the reflection of what took place in Job 1-2 with God, the adversary, and Job. While it does not say anything about an event taking place in the divine court, we get a snapshot there of Satan's manipulative ways and his desire to see God's faithful disproved and shown shallow in their level of commitment to God. Just as God does not unleash Satan on the world to do evil things at his behest (he only extends a limited permission for Satan to do something that ultimately results in giving God honor, as Job's reaction to all of his trials does), here in 1 Chronicles, Satan is shown as actively involved against the Lord's anointed king. Behind the scenes, we don't know what transpired, how Satan introduced this idea for the census or if he only energized David's desire to carry it out. 1 Chronicles 2:1 does, however, tell us that there was more going on than just David acting as king. There was a being involved behind the scenes who helped bring this desire to fruition. When we read in 2 Samuel about God's involvement, we can deduce that he deferred to this sinful request and allowed David to carry out the census, even though it did not please him. Because God saw that David had reasoned in his mind to execute this plan (instead of, perhaps, seeking one of the prophets to inquire of the Lord what he should do, or simply not do it at all), God said, "Go, do it." The very expression "anger of the LORD" tells us that this was not a plan that originated with God. He was angry because David wanted to do it, and by doing so was trusting in what he could count, not in what God could do no matter what the numbers were. The two texts together help us understand a fuller picture of what was transpiring during these days of David's reign.
That leads us to another point. That there is an evil being on the loose in the world is not an evolved concept in Hebrew thought and literature. The earliest of the Old Testament writings, Job, presents this accuser and allows readers to see his destructive nature. A straightforward reading of the Job passages does not present an ally of God, but the opposite. Beyond that, the Old Testament attributes the fall of Adam and Eve and the introduction of death into the world with the serpent in Genesis 3. The passage in 1 Chron. 2:1 shows us that one of this serpent's names is actually "Satan," not just a description of what type of being he is.