The adversary in Job
Whether the figure who accuses Job is a heavenly prosecutor, an independent adversary, or a literary device.
Job 1:6-12
6Now on the day when God’s sons came to present themselves before Yahweh, Satan also came among them.
7Yahweh said to Satan, “Where have you come from?” Then Satan answered Yahweh, and said, “From going back and forth in the earth, and from walking up and down in it.”
8Yahweh said to Satan, “Have you considered my servant, Job? For there is no one like him in the earth, a blameless and an upright man, one who fears God, and turns away from evil.”
9Then Satan answered Yahweh, and said, “Does Job fear God for nothing?
10Haven’t you made a hedge around him, and around his house, and around all that he has, on every side? You have blessed the work of his hands, and his substance is increased in the land.
11But stretch out your hand now, and touch all that he has, and he will renounce you to your face.”
12Yahweh said to Satan, “Behold, all that he has is in your power. Only on himself don’t stretch out your hand.” So Satan went out from the presence of Yahweh.
What each tradition says
Rabbinic / Midrashic
The Jewish Encyclopedia identifies Satan as the celestial prosecutor, who sees only iniquity. He persists in his evil opinion of Job even after Job successfully endures his first trial by surrendering to God's will. Satan then demands another test through physical suffering.
Joseph Jacobs and Ludwig Blau, The Jewish Encyclopedia, s.v. 'Satan' (New York: Funk & Wagnalls, 1901-1906) — Section 'In the Bible' (the prologue of Job)
Patristic
Gregory the Great says Satan had no power against him to tempt him, except by the Lord's permission. Therefore Job does not say, "The Lord hath given, the devil hath taken away," but "The Lord gave, the Lord hath taken away." He attributes the taking to the Lord, not to Satan.
Gregory the Great, Morals on the Book of Job, vol. I (Library of Fathers of the Holy Catholic Church, Oxford, 1844); archive.org scan — On Job 1:21, within the exposition of Job 1
Catholic
Haydock reads Job 1:6 as a figure accommodated to human understanding. It shows Satan's restless efforts against God's servants, his inability to act without God's permission, and God's limit on temptation. God assists by grace, so the enemy's vain efforts only display the servants' virtue and increase their merit.
George Leo Haydock, George Haydock's Catholic Bible Commentary (1859), on Job 1:6 (bibliaplus.org edition) — Comment on Job 1:6 (Challoner)
Orthodox
No sourced position found. Searched the CCEL ANF/NPNF texts (ANF 6-7, NPNF ser. 1 vols. 4, 11) for the Eastern fathers on Job's adversary - none; pravoslavieto.com Philaret Longer Catechism Q. 107-110 defines the devil as a slanderer and fallen angel but says nothing of Job 1:6; archive.org PD English scans (Olympiodorus, Hesychius) are modern copyrighted translations. No PD Orthodox statement on the Job 1:6 figure found.
Reformed / Protestant
Henry allows that the discourse between God and Satan in these verses may be parabolical, like Micaiah's, or an allegory. It represents the devil's malice against good men and the divine check and restraint upon that malice, intimating that earthly affairs are much the subject of the unseen world's counsels.
Matthew Henry, Commentary on the Whole Bible, Volume III (Job to Song of Solomon) (CCEL) — Exposition of Job 1:6-12
Evangelical
Wesley says Job 1:6 is not to be understood literally. It is a parabolical representation of the truth that God, by his wise and holy providence, governs all the actions of men and devils, condescending to human capacity and speaking in the language of the sons of men.
John Wesley, Explanatory Notes upon the Old Testament - Notes on the Book of Job (Wesley Center Online text) — Note on Job 1:6