a) He Regenerates the Believer.
John 3:3-5—"Born of … the Spirit." Tit. 3:5—"The… renewing of the Holy Ghost." Sonship, and membership in the kingdom of God, come only through the regenerating of the Holy Spirit. "It is the Spirit that quickeneth." Just as Jesus was begotten of the Holy Ghost, so must every child of God who is to be an heir to the kingdom.
b) The Spirit Indwells the Believer.
1 Cor. 6:19—"Your body is the temple of the Holy Ghost which is in you." Also 3:16; Rom. 8:9. Every believer, no matter how weak and imperfect he may be, or how immature his Christian experience, still has the indwelling of the Spirit. Acts 19:2 does not contradict this statement. Evidently some miraculous outpouring of the Spirit is intended there, the which followed the prayer and laying on of the hands of the apostles. "Now if any man have not the Spirit of Christ, he is none of his." "No man can say that Jesus is the Lord, but by the Holy Ghost" (Rom. 8:9; 1 Cor. 12:3).
c) The Spirit Seals the Believer with Assurance of Salvation.
Eph. 1:13, 14—"In whom also after that ye believed, ye were sealed with that Holy Spirit of promise; which is the earnest of our inheritance." Also 4:30—"Sealed unto the day of redemption." This sealing stands for two things: ownership and likeness (2 Tim. 2:19-21). The Holy Spirit is "the Spirit of adoption" which God puts into our hearts, by which we know that we are His children. The Spirit bears witness to this great truth (Gal. 4:6; Rom. 8:14, 16). This sealing has to do with the heart and the conscience—satisfying both as to the settlement of the sin and sonship question.
d) The Holy Spirit Infills the Believer.
Acts 2:4—"And they were all filled with the Holy Ghost." Eph. 5:18—"Be filled with the Spirit." The filling differs somewhat from the indwelling. We may speak of the baptism of the Spirit as that initial act of the Spirit by which, at the moment of our regeneration, we are baptized by the Spirit into the body of Christ; the Spirit then comes and takes up His dwelling within the believer. The filling with the Spirit, however, is not confined to one experience, or to any one point of time exclusively; it may be repeated times without number. There is one baptism, but many infillings with the Spirit. The experience of the apostles in the Acts bears witness to the fact that they were repeatedly filled with the Spirit. Whenever a new emergency arose they sought a fresh infilling with the Spirit (cf. Acts 2:4 with 4:31 showing that the apostles who were filled on the day of Pentecost were again filled a few days after).
There is a difference between possessing the Spirit, and being filled with the Spirit. All Christians have the first; not all have the second, although all may have. Eph. 4:30 speaks of believers as being "sealed," whereas 5:18 commands those same believers to "be filled (to be being filled again and again) with the Spirit."
Both the baptism and the infilling may take place at once. There need be no long wilderness experience in the life of the believer. It is the will of God that we should be filled (or, if you prefer the expression, "be baptized") with the Spirit at the moment of conversion, and remain filled all the time. Whenever we are called upon for any special service, or for any new emergency, we should seek a fresh infilling of the Spirit, either for life or service, as the case may be.