Once the Holy Spirit enters a person, can He leave? In Psa 51, David prayed:

Do not cast me away from Your presence, and do not take Your Holy Spirit from me (Psa 51:11).

The Bible gives the example of the Holy Spirit leaving Samson:

And she said, "The Philistines are upon you, Samson!" So he awoke, from his sleep, and said, "I will go out as before, at other times, and shake myself free!" But he did not know that the Lord had departed from him (Jdg 16:20).

In another instance, the Holy Spirit is said to have left Saul:

But the Spirit of the Lord departed from Saul, and a distressing spirit from the Lord troubled him (1Sa 16:14).

These passages seem to teach that one can lose the Holy Spirit. But this is not necessarily the case. There are other possible solutions to this question. Some believe that the situations of David, Samson, and Saul must be understood in their Old Testament context. It appears that during that period, the Holy Spirit did not indwell believers on a permanent basis; but rather His presence in the life of the believer was of a limited duration.

Special Anointing

A second view holds that it was not the indwelling of the Holy Spirit that left these people, but a particular anointing or empowering of the Spirit that departed. David and Saul were kings and had a special anointing from God to rule the people. Samson also had a special anointing from God to lead Israel. What left Samson and Saul and what David prayed to retain was not the indwelling of the Holy Spirit but rather the Holy Spirit's anointing to rule. In the same way, the Holy Spirit always indwells a believer, but can anoint that New Testament believer for a specific and temporary purpose.

Whatever the case may be, the New Testament makes it plain that the Holy Spirit will not leave the believer.

And I will pray the Father, and He will give you another Helper, that He may abide with you forever (Jhn 14:16).

Having believed, you were sealed with the Holy Spirit of promise, who is the guarantee of our inheritance until the redemption of the purchased possession (Eph 1:13-14).