Satan, also known as the Devil, and sometimes also called Lucifer in Christianity, is an entity in Abrahamic religions that seduces humans into sin or falsehood. In Judaism, Satan is seen as an agent subservient to God, typically regarded as a metaphor for the yetzer hara, or “evil inclination”. In Christianity and Islam, he is usually seen as a fallen angel or jinn who has rebelled against God, who nevertheless allows him temporary power over the fallen world and a host of demons. In the Quran, Shaitan, also known as Iblis, is an entity made of fire who was cast out of Heaven because he refused to bow before the newly created Adam and incites humans to sin by infecting their minds with waswās (“evil suggestions”).

A figure known as ha-satan (“the satan”) first appears in the Hebrew Bible as a heavenly prosecutor, subordinate to Yahweh (God), who prosecutes the nation of Judah in the heavenly court and tests the loyalty of Yahweh’s followers.[citation needed] During the intertestamental period, possibly due to influence from the Zoroastrian figure of Angra Mainyu, the satan developed into a malevolent entity with abhorrent qualities in dualistic opposition to God. In the apocryphal Book of Jubilees, Yahweh grants the satan (referred to as Mastema) authority over a group of fallen angels, or their offspring, to tempt humans to sin and punish them.

Although the Book of Genesis does not mention him, Christians often identify the serpent in the Garden of Eden as Satan. In the Synoptic Gospels, Satan tempts Jesus in the desert and is identified as the cause of illness and temptation. In the Book of Revelation, Satan appears as a Great Red Dragon, who is defeated by Michael the Archangel and cast down from Heaven. He is later bound for one thousand years, but is briefly set free before being ultimately defeated and cast into the Lake of Fire.

In the Middle Ages, Satan played a minimal role in Christian theology and was used as a comic relief figure in mystery plays. During the early modern period, Satan’s significance greatly increased as beliefs such as demonic possession and witchcraft became more prevalent. During the Age of Enlightenment, belief in the existence of Satan was harshly criticized by thinkers such as Voltaire. Nonetheless, belief in Satan has persisted, particularly in the Americas.

Although Satan is generally viewed as evil, some groups have very different beliefs. In theistic Satanism, Satan is considered a deity who is either worshipped or revered. In LaVeyan Satanism, Satan is a symbol of virtuous characteristics and liberty. Satan’s appearance is never described in the Bible, but, since the ninth century, he has often been shown in Christian art with horns, cloven hooves, unusually hairy legs, and a tail, often naked and holding a pitchfork. These are an amalgam of traits derived from various pagan deities, including Pan, Poseidon, and Bes. Satan appears frequently in Christian literature, most notably in Dante Alighieri’s Inferno, all variants of the classic Faust story, John Milton’s Paradise Lost and Paradise Regained, and the poems of William Blake. He continues to appear in film, television, and music.

Hebrew Bible: Balaam and the Angel (1836) by Gustav Jäger. The angel in this incident is referred to as a “satan”.
The Hebrew term śāṭān (Hebrew: שָׂטָן) is a generic noun meaning “accuser” or “adversary”, and is derived from a verb meaning primarily “to obstruct, oppose”. In the earlier biblical books, e.g. 1 Samuel 29:4, it refers to human adversaries, but in the later books, especially Job 1-2 and Zechariah 3, to a supernatural entity. When used without the definite article (simply satan), it can refer to any accuser, but when it is used with the definite article (ha-satan), it usually refers specifically to the heavenly accuser, literally, the satan.

The word with the definite article Ha-Satan (Hebrew: הַשָּׂטָן hasSāṭān) occurs 17 times in the Masoretic Text, in two books of the Hebrew Bible: Job ch. 1–2 (14×) and Zechariah 3:1–2 (3×). It is translated in English bibles mostly as ‘Satan’.

The word without the definite article is used in ten instances, of which two are translated diabolos in the Septuagint. It is generally translated in English Bibles as ‘an accuser’ (1x) or ‘an adversary’ (9x as in Book of Numbers, 1 & 2 Samuel and 1 Kings). In some cases, it is translated as ‘Satan’:

1 Chronicles 21:1, “Satan stood up against Israel” (KJV) or “And there standeth up an adversary against Israel” (Young’s Literal Translation) Psalm 109:6b “and let Satan stand at his right hand” (KJV) or “let an accuser stand at his right hand.” (ESV, etc.)

The word does not occur in the Book of Genesis, which mentions only a talking serpent and does not identify the serpent with any supernatural entity. The first occurrence of the word “satan” in the Hebrew Bible in reference to a supernatural figure comes from Numbers 22:22, which describes the Angel of Yahweh confronting Balaam on his donkey: “Balaam’s departure aroused the wrath of Elohim, and the Angel of Yahweh stood in the road as a satan against him.” In 2 Samuel 24, Yahweh sends the “Angel of Yahweh” to inflict a plague against Israel for three days, killing 70,000 people as punishment for David having taken a census without his approval. 1 Chronicles 21:1 repeats this story, but replaces the “Angel of Yahweh” with an entity referred to as “a satan”.

Some passages clearly refer to the satan, without using the word itself. 1 Samuel 2:12 describes the sons of Eli as “sons of Belial”; the later usage of this word makes it clearly a synonym for “satan”. In 1 Samuel 16:14–2, Yahweh sends a “troubling spirit” to torment King Saul as a mechanism to ingratiate David with the king. In 1 Kings 22:19–25, the prophet Micaiah describes to King Ahab a vision of Yahweh sitting on his throne surrounded by the Host of Heaven. Yahweh asks the Host which of them will lead Ahab astray. A “spirit”, whose name is not specified, but who is analogous to the satan, volunteers to be “a Lying Spirit in the mouth of all his Prophets”.