Can a Christian be indwelled by a demon? For example, when Jesus called Peter "Satan" in Matthew 16, did that indicate Peter was possessed by a demon or Satan?
In Matthew’s Gospel we read:
Matt. 16:21 From that time Jesus began to show His disciples that He must go to Jerusalem, and suffer many things from the elders and chief priests and scribes, and be killed, and be raised up on the third day.
Matt. 16:22 Peter took Him aside and began to rebuke Him, saying, “ God forbid it, Lord! This shall never happen to You.”
Matt. 16:23 But He turned and said to Peter, “Get behind Me, Satan! You are a stumbling block to Me; for you are not setting your mind on God’s interests, but man’s.”
In this exchange, Jesus responded to Peter’s suggestion that He not go forward with the Father's plan to send His Son to die on the cross. Obviously, Peter didn't understand what he was saying, nevertheless Jesus rebuked Peter for tempting Him to disobey the Father. Jesus told Peter his advice furthered the desires and purposes of Satan rather than the Father.
By the context, we see that when Jesus said to Peter, “Get behind Me, Satan,” Jesus wasn’t literally addressing Peter as if Satan were resident in Peter’s body. Rather, Jesus was calling Peter Satan to teach Peter that his desires supported Satan's purposes. Perhaps also Jesus was indicating that Satan was behind the scenes influencing Peter’s thinking and words. In either case, Jesus meant that Peter was not speaking by the Spirit nor was He speaking in agreement with the word of God. Rather, Peter was echoing the words and purposes of Satan.
This example reminds us that believers can unknowingly support Satan's goals by living in our flesh and not by the Spirit. Furthermore, all people (whether believer or unbeliever) can be manipulated by Satan without necessarily requiring that a demon indwell a person. The enemy is very powerful, and his power includes tempting believers, delivering false teaching, and even influencing our thoughts and emotions in opposition to God.
None of these influences requires an indwelling. Scriptures say that every believer can be tempted by Satan or even taught by him. For example:
1Cor. 7:5 Stop depriving one another, except by agreement for a time, so that you may devote yourselves to prayer, and come together again so that Satan will not tempt you because of your lack of self-control.
1Cor. 10:13 No temptation has overtaken you but such as is common to man; and God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will provide the way of escape also, so that you will be able to endure it.
1Th. 3:5 For this reason, when I could endure it no longer, I also sent to find out about your faith, for fear that the tempter might have tempted you, and our labor would be in vain.
1Tim. 6:9 But those who want to get rich fall into temptation and a snare and many foolish and harmful desires which plunge men into ruin and destruction.
2Cor. 2:10 But one whom you forgive anything, I forgive also; for indeed what I have forgiven, if I have forgiven anything, I did it for your sakes in the presence of Christ,
2Cor. 2:11 so that no advantage would be taken of us by Satan, for we are not ignorant of his schemes.
Finally, scripture teaches that once the Holy Spirit resides in our bodies (because of our faith in Jesus Christ), we are forever sealed by the Holy Spirit and no longer accessible to the enemy for indwelling:
Matt. 12:43 “ Now when the unclean spirit goes out of a man, it passes through waterless places seeking rest, and does not find it.
Matt. 12:44 “Then it says, ‘I will return to my house from which I came’; and when it comes, it finds it unoccupied, swept, and put in order.
Matt. 12:45 “Then it goes and takes along with it seven other spirits more wicked than itself, and they go in and live there; and the last state of that man becomes worse than the first. That is the way it will also be with this evil generation.”
Jesus was explaining that were God to free someone from demon possession yet not deliver saving faith, He would have done little to help them. As long as a person remains “unoccupied” by the absence of the Holy Spirit (which is the case for all unbelievers), then that person will be available to host the enemy’s agents. Only if a body becomes occupied (e.g., indwelled by the Holy Spirit) is that person safe from the enemy ever returning to set up a home in the body again.
By logical deduction, we must also conclude that once we become a Christian, we are no longer susceptible to demon possession, though the enemy can still tempt, deceive and influence us in negative ways when we live in the flesh and not in the Spirit.