The Greek word baptizo has two meanings, one literal and the other figurative. The word literally means, “to submerge,” but the figuratively meaning is ” to be identified with.” The baptism of the Spirit is that act of God by which He identifies believers with the exalted Head of the church, Jesus Christ, and formed the spiritual body of Christ on earth (1 Cor. 12:12-14). Historically, this took place at Pentecost; today, it takes place whenever a sinner trusts Jesus Christ and is born again.
When you read about “baptism” in the New Testament, you must exercise discernment to determine whether the word is to be interpreted literally or symbolically. For example, in Romans 6:3-4 and Galatians 3:27-28, the reference is symbolic since water baptism cannot put a sinner into Jesus Christ. Only the Holy Spirit can do that (Rom. 8:9, Cor. 12:13, see Acts 10:44-48). Water baptism is a public witness of the person’s identification with Jesus Christ, while Spirit baptism is the personal and private experience that identifies that person with Christ.
It is important to note that historically; the baptism of the Spirit took place in two stages; the Jewish believers were baptized at Pentecost, and the Gentiles were added to the body in the home of Cornelius (Acts 10:44-48, 11:15-17, and see Eph. 2:11-22).
The filling of the Spirit has to do with power for witness and service (Acts 1:8). We are not exhorted to be baptized by the Spirit, for this is something God does once and for all when we trust His Son. But we are commanded to be filled with the Spirit (Eph. 5:18), for we need His power constantly if we are to serve God effectively. At Pentecost, the Christians were filled with the Spirit and experienced the baptism of the Spirit; but after that, they experienced many fillings (Acts 4:8, 31, 9:17, 13:9) but no more baptisms.
Occasionally someone says, “What difference does it make what words we use? The important thing is that we have the experience!” I doubt that they would apply that approach to any other area of life such as medicine, cooking, or mechanics. What difference does it make if the pharmacist uses arsenic or aspirin in the prescription, just so long as you get well? Or if the mechanic installs an alternator or a carburetor, just so long as the car works?
The Holy Spirit has revealed God’s truth to us in words (1 Cor. 2:12-13), and these words have definite meanings that must not be changed. Regeneration must not be confused with justification, nor propitiation with adoption. Each of these words is important in God’s plan of salvation and must be defined accurately and used carefully.
The baptism of the Spirit means that I belong to His body; the fullness of the Spirit means that my body belongs to Him. The baptism is final; the fullness is repeated, as we trust God for new power to witness. The baptism involves all other believers, for it makes us one in the body of Christ (Eph. 4:1-6); while the fullness is personal and individual. These are two distinct experiences and they must not be confused.
(See, Warren Wiersbe, The Bible Exposition Commentary, pg. 407-408)