This is a thread I posted on another board, the subject was can a Christian loose the Holy Spirit. But since this also applies to Salvation, I thought it might be something to consider here.
My son and I have discussed this subject before - here are some of the conclusions we came to.
The Holy Spirit is given to the believer as a permanent seal of Salvation.
Eph 4:30
30: And grieve not the holy Spirit of God, whereby ye are sealed unto the day of redemption.
KJV
Some have gotten the mistaken idea from David’s prayer in Psalms that Gods spirit could be removed.
Ps 51:11
11: Cast me not away from thy presence; and take not thy holy spirit from me.
KJV
This prayer was David’s confession, and repentance of his sin with Bathsheba. It was a prayer for the restoration of fellowship, and the previous joy, and power of the Holy Spirit’s working in his life, that God would not hide his face or turn his back on him.
Take a look at another example Lot who dwelled in Sodom, and daily vexed the spirit by the things he saw and heard. The spirit was not taken from him, otherwise he would not have been considered a Godly Righteous man. But God rather delivered him out of his circumstances.
2 Peter 2:8
8: (For that righteous man dwelling among them, in seeing and hearing, vexed his righteous soul from day to day with their unlawful deeds)
9: The Lord knoweth how to deliver the godly out of temptations, and to reserve the unjust unto the day of judgment to be punished:
KJV
There is one circumstance where it might be thought that Gods spirit has been removed from a person, when in fact they never had it.
Matt 7:21-23
21: Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
22: Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
23: And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
KJV
These are those who have professed faith in Christ but did not have any true commitment to him. When a person is truly saved his life will change in some way, it may not be a complete overhaul from the beginning, but some evidence of their sincerity will be manifest. Those who profess faith, and continue on with life as usual, and have no remorse for sin are not saved.
No one who is truly indwelt with the spirit of God can sin, without constant feelings of guilt, and remorse for their sinfulness. Some spiritual fruit will be evident in the lives of those who do believe. And should become more evident as their fellowship with the Spirit becomes greater.
John 15:2
2: Every branch in me that beareth not fruit he taketh away: and every branch that beareth fruit, he purgeth it, that it may bring forth more fruit.
KJV
This verse is a comparison of the righteous, and the unrighteous. Those who are true will over time produce more fruit, those who are false will have their folly revealed. Their sins will be laid bare, and that which they seem to have will be removed, the veil of covering will be rent.
Matt 25:29
29: For unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath.
KJV
So the person who is truly saved will never loose the spirit, or have it taken away. But those who have a profession, and no possession who never had the spirit; may seem to some they have had the spirit taken away, but in truth never had it to loose in the first place.