From Anstey’s Doctrinal Definitions:
The baptism of the Holy Spirit is mentioned seven times in Scripture (Matt. 3:11; Mark 1:8; Luke 3:16; John 1:33; Acts 1:5; 11:16; 1 Cor. 12:13). It refers to the Spirit’s work of forming the body of Christ. This was accomplished by the Lord when he sent the Spirit down from heaven on the day of Pentecost and linked the believers in the upper room in Jerusalem into one body by the Spirit’s indwelling (Acts 2:1-4, 33). This was extended later to take in believing Gentiles (Acts 11:1-18). Once this was done, the Spirit’s work of baptizing was complete for all time. It will never be repeated. 1 Corinthians 12:12-13 confirms this, referring to that event in the aorist tense (in the Greek), which means that it was a once-and-for-all act. Hence, the Spirit of God is not baptizing today; if He were, then there would be many bodies of Christ on earth, because the sole purpose of the baptism of the Spirit was to form the body of Christ. This, of course, could not be so, because Scripture states emphatically, “There is one body” (Eph. 4:4).
A closer look at the seven references in Scripture to the baptism of the Spirit will show that it is an historical act, and not something the Spirit is doing today. Five of these references look forward in time to this action of the Spirit, being that they were uttered before Pentecost (Matt. 3:11; Mark 1:8; Luke 3:16; John 1:33; Acts 1:5). The sixth and seventh references to the baptism of the Spirit were uttered after Pentecost (Acts 11:16; 1 Cor. 12:13), and point backward in time to something that the Spirit did. Since there is no other thing concerning the Holy Spirit in Scripture that took place between these two groups of references, they would have to be referring to the Spirit’s coming on the day of Pentecost to form the body of Christ.
There are two main misconceptions concerning the baptism of the Holy Spirit. The first is what we might call the "Pentecostal" or "Charismatic" view. Christians who have this idea see the baptism of the Spirit as being a personal experience that a believer has sometime after he is saved, whereby he is filled with the Spirit, and thus is enabled to speak with tongues, etc. However, in Scripture, the baptism of the Holy Spirit is never mentioned as happening to someone individually; it was purely a corporate action of linking the company of 120 believers in the upper room in Jerusalem into one unit by His indwelling.
The second view is the mainline evangelical "non-charismatic" view. Christians who hold this idea think that the baptism of the Holy Spirit occurs when a person believes on the Lord Jesus Christ and thereby receives the Spirit, and thus made part of the body of Christ. However, this is not correct either. Note carefully that 1 Corinthians 12:13 does not say, “We have been baptized into the one body.” Adding the article “the” changes the meaning considerably. It supposes that the body was in existence before the baptism mentioned in the verse took place. This would support this mistaken idea; however, the verse doesn’t say that. It says, "baptized into one body,” meaning that the baptism is what formed the one body. Thus, the baptism of the Spirit is a historical event. All who get saved thereafter are added to that body by the sealing of the Spirit (Eph. 1:13).
We might wonder how it is that Paul could speak of himself (and of the Corinthians) as being baptized by the Spirit, when they were not even saved when the Spirit came down and formed the body of Christ at Pentecost. The answer is that Paul was speaking representatively. He said, “We”—referring to the Christian company as a whole—“have been baptized into one body,” referring back to the action of the Spirit at Pentecost. It is something like the incorporation of a company. It is incorporated once, and each time the company takes on a new employee it does not need to be incorporated again. Nor is there any such thing as every new employee in the company being incorporated; the new employee is merely added to an already-incorporated company. Likewise, when someone gets saved today, he is added by the indwelling presence of the Spirit to an already-baptized body. As mentioned, this is called the sealing of the Spirit (Eph. 1:13; 2 Cor. 1:21-22).
Taking our illustration a little further, suppose we listened in on a company’s board meeting and heard one of the directors say, “We were incorporated 100 years ago.” We would have no trouble understanding what he meant, but someone who doesn’t understand the English language very well might ask, “What does that person mean? None of these people in this meeting are over 60 years of age. How can he say, ‘We ... a hundred years ago ... ?’” Well, it’s because the director was speaking representatively of the company. Likewise, being part of the Christian company that was baptized at Pentecost, Paul and the Corinthians (and we too) are embraced in that baptism.
W. Scott said, "The baptizing of all believers into one body is a corporate act and never repeated. As the result of this spiritual baptism, the one body is formed, and into this Spirit-baptized body believers find themselves when sealed by God" (Some New Testament Teachings, p. 174).
Another expositor in Scripture Truth magazine said, "Let us look now at some of the actions attributed to the Holy Spirit. First of all, we learn that He baptizes. Scripture shows clearly that this baptism is an accomplished historical fact, which took place once and for all at Pentecost" (Scripture Truth, vol. 21, p. 102).
J. N. Darby said, "As to a person subsequent to Pentecost being baptised with the Holy Ghost, I should say he was introduced into an already-baptised body" (Letters, vol. 3, p. 466).
F. G. Patterson said, "The Holy Ghost baptized them into 'one body.' Here let me say, that an individual is not said to be baptized with the Holy Ghost in Scripture. Not even the Lord Himself" (The Church of God, the Body of Christ, p. 27).
W. T. P. Wolston said, "If the baptism of the Holy Ghost has taken place at Pentecost, does Scripture carry the thought that it is ever to be repeated? I believe distinctly not. The Holy Ghost has come; He is here. The baptism of the Holy Spirit has been received, and there is, consequently, no fresh baptism to be looked for" (Another Comforter, p. 226). He also said, "The baptism of the Holy Ghost took place once, and once only, so far as I read of it in Scripture."
Hence, the baptism of the Spirit is not something that is going on today as a post-salvation experience, nor is it what brings believers into the body of Christ. It was a historical action of the Spirit that has been long completed, and never to be repeated.