Satan is primarily understood as an "accuser" or "adversary" in the Hebrew Bible, and is not necessarily the personification of evil that he would become in later Abrahamic religions. In the New Testament, Satan is a name that refers to a decidedly malevolent entity (devil) who possesses demonic god-like qualities....
The original Hebrew term,
satan, is a noun from a verb meaning primarily to, “obstruct, oppose,” as it is found in Numbers 22:22, 1 Samuel 29:4, Psalms 109:6.
Ha-Satan is traditionally translated as “the accuser,” or “the adversary.” The definite article “ha-” ( English: “the"), is used to show that this is a
title bestowed on a being, versus the
name of a being. Thus this being would be referred to as “the satan.”
In the Book of Job, ha-Satan is a member of the Divine Council, "the sons of God" who are subservient to God. Ha-Satan, in this capacity, is many times translated as "the prosecutor", and is charged by God to tempt humans and to report back to God all who go against His decrees.
...scholars see contact with religious dualism in Babylon, and early Zoroastrianism in particular, as having influenced Second Temple period Judaism, and consequently early Christianity. Subsequent development of Satan as a "deceiver" has parallels with the evil spirit in Zoroastrianism, known as "the Lie", who directs the forces of darkness.