I stand in awe that some people believe that Christians can be possessed with devils.
Jessie Penn Lewis in her book The War on the Saints claims that Christians can be possessed with devils.
In chapter 12 of her book, Lewis says:
To put it in bluntest language, the Revival hour is the occasion for evil spirits to obtain “possession” of spiritual believers, and REVIVAL CEASES BECAUSE OF SUCH POSSESSION. The most spiritual believers, baptized with the Holy Spirit, and most fitted to be used of God in Revival service, may become deceived and possessed by evil spirits in their outer being THROUGH ACCEPTING THE COUNTERFEITS OF SATAN. Believers who are not so abandoned to the Spirit escape the acute “possession, ” but in their contact with hitherto unknown workings from the spiritual realm, are equally open to deception which is manifested in a less recognizable way.
However the Scriptures clearly testify of the liberty the believers have from such devilish possession.
Jesus said that “I cast out devils by the Spirit of God, then the kingdom of God is come unto you” (Matthew 12:28).
We know that those who are possessed by devils in are bondage to do their will. The scriptures testify of the liberty of believers insisting that they cannot be possessed with devils.
 And you hath he quickened, who were dead in trespasses and sins;
 Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience:
 Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others.
 But God, who is rich in mercy, for his great love wherewith he loved us,
 Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;)
 And hath raised us up together, and made us sit together in heavenly places in Christ Jesus:
 That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus.
 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
 Not of works, lest any man should boast.
If a believer can be possessed and subjected to the god of this world, then what is the believer saved from?
The apostle Paul addresses the state of the believer in Romans 6:9-23.
9] Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
 For in that he died, he died unto sin once: but in that he liveth, he liveth unto God.
 Likewise reckon ye also yourselves to be dead indeed unto sin, but alive unto God through Jesus Christ our Lord.
 Let not sin therefore reign in your mortal body, that ye should obey it in the lusts thereof.
 Neither yield ye your members as instruments of unrighteousness unto sin: but yield yourselves unto God, as those that are alive from the dead, and your members as instruments of righteousness unto God.
 For sin shall not have dominion over you: for ye are not under the law, but under grace.
 What then? shall we sin, because we are not under the law, but under grace? God forbid.
 Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?
 But God be thanked, that ye were the servants of sin, but ye have obeyed from the heart that form of doctrine which was delivered you.
 Being then made free from sin, ye became the servants of righteousness.
 I speak after the manner of men because of the infirmity of your flesh: for as ye have yielded your members servants to uncleanness and to iniquity unto iniquity; even so now yield your members servants to righteousness unto holiness.
 For when ye were the servants of sin, ye were free from righteousness.
 What fruit had ye then in those things whereof ye are now ashamed? for the end of those things is death.
 But now being made free from sin, and become servants to God, ye have your fruit unto holiness, and the end everlasting life.
 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
It is clear that Christians are no longer slaves to sin which also implies that they cannot be made slaves by devil possession.
Christians are instructed to walk in the Spirit. But how can believers walk in the Spirit if they are subject to the whims of evil spirits?
 But if ye be led of the Spirit, ye are not under the law.
 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,
 Meekness, temperance: against such there is no law.
 And they that are Christ’s have crucified the flesh with the affections and lusts.
 If we live in the Spirit, let us also walk in the Spirit.
 Let us not be desirous of vain glory, provoking one another, envying one another.
We know that nothing can separate a believer from the love of God. It must follow that the believer cannot be possessed by a devil. For this would separate him from God and Jesus Christ his saviour.
 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
2 Corinthians 3:17-18
 Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty.
 But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord.