What does the Bible say about unclean spirits?

from the old testament

• God is holy (Isaiah 6:3) and cannot dwell with the unholy (Habakkuk 1:13). In His relationship with Israel, He set rules regarding uncleanliness. These were not rules about how to be morally pure nor were they describing what was sinful. Rather, they were rules about how an unclean thing or person could be made ritually clean so it could be in God's presence.
• God described certain things as always impure, including specific types of animals (Leviticus 11:4–8). They were considered unclean because God wanted the Israelites to stay away from them to separate themselves from the surrounding pagans—there was nothing inherently wrong with the animals themselves.
• There were other things that could be either unclean or clean. For example, instruments that entered God’s temple needed to be ritually made clean before entering (Numbers 7:1). Yet, the same instrument could become unclean if it were mishandled or dropped (Leviticus 11:32). Similarly, people could also be considered unclean (Leviticus 15:2), but they could be ritually made clean (Leviticus 15:13). Being unclean or clean didn’t refer to one’s moral guilt. It referred to whether God considered the thing or person ritually fit to be within the camp, or even closer, near Him.
• Though the term is used more often in the New Testament, the Old Testament also occasionally referred to demons as unclean spirits. For example, speaking about the future, God said, “I will also remove the prophets and the unclean spirit from the land” (Zechariah 13:1, NASB).

from the new testament

• Demons are unclean, unable to dwell with God because they are evil and impure. Thus, while uncleanliness refers to their ritual impurity, they are considered unclean because of their moral impurity. The fact that an “unclean spirit” is the same thing as a “demon” can be seen in Revelation 16:13–14, which reads, “I saw, coming out of the mouth of the dragon and out of the mouth of the beast and out of the mouth of the false prophet, three unclean spirits like frogs. For they are demonic spirits ….” Being demonic and being unclean are interchangeable, though “unclean spirit” is used to draw out their impurity in contrast to God, His Spirit, and holy angels.
• Unclean spirits can inhabit people (Mark 5:2). We refer to it as demon-possession, but it doesn’t always mean that the demon is in full control. For example, in Mark 5:1–13, the demon-possessed man shifts in his speech from “we” (the demons) to “I” and “me” (the man). When demons possess someone, they often torment them (Mark 9:17–18). However, because they coexist, they don’t always interfere, even allowing the unbeliever to participate in religious ceremonies (Mark 1:23).
• Unclean spirits are noted for their great strength (Mark 5:3–4; Acts 19:16). Yet, despite their raw power, even thousands of them fall at a single word from Jesus because His authority far exceeds theirs (Mark 1:27; 5:8).
• Given Jesus’ authority and the fact that His Spirit indwells believers (Romans 8:9), believers do not need to fear unclean spirits. The Holy Spirit is greater than them (1 John 4:4) and will not share space with uncleanliness, just like God required ritual purity for everything and everyone who entered His temple in the Old Testament.

implications for today

In the West, demonic activity is not always as obvious as it was in the first century, when people accepted possession as an unfortunate part of life. But that doesn’t mean unclean spirits are no longer around. Until Jesus returns, the world remains under Satan’s influence (1 John 5:19), which includes his demons being at work. However, believers don’t need to worry about them because they can’t do us eternal harm (Romans 37–39). Additionally, believers are not called to identify what sinful behavior in others might be from an unclean spirit. That is because, while demonic activity is real, Scripture teaches that human beings are perfectly capable of the most egregious sins all by themselves.

Therefore, rather than being worried about unclean spirits, we need to be concerned about unclean people. Scripture teaches that everyone is unclean (sinful) and, left to their own, will face God’s eternal wrath (Revelation 20:15). Jesus came to die for sinners so that when someone repents of their sin and trusts in Him, He cleanses them of all unrighteousness (1 John 1:9). Proclaiming that good news is to be our focus.

In His good timing, God will deal with the unclean spirits, and He will deal with the unrepentant people. But right now, He allows both to continue so that we, His children, have the opportunity to tell those who are still unclean about how Jesus made us clean!