Are you saying that people don't get baptized in the Holy Spirit anymore? If this is so, then what is it called when people are filled with the Holy Spirit? Like I have seen people get prayed for and they will shake and fall to the ground because of the power of God. What does the Bible say about this?
There are only two recorded incidences of people being baptized by the Holy Spirit. The first is recorded at the beginning of Acts 2 when the apostles received the Spirit. The second is recorded at the end of Acts 10 when Cornelius and his household received the Spirit to prove that God accepted the Gentiles as saved without first becoming Jews. Peter emphasized that the event experienced by Cornelius and his household was the same thing that had happened at the beginning of the church. "And as I began to speak, the Holy Spirit fell upon them, as upon us at the beginning. Then I remembered the word of the Lord, how He said, 'John indeed baptized with water, but you shall be baptized with the Holy Spirit.' If therefore God gave them the same gift as He gave us when we believed on the Lord Jesus Christ, who was I that I could withstand God?" (Acts 11:15-17).
The event that happened on the day of Pentecost was not common place. The fact that the experience of Cornelius reminded Peter of what happened at the beginning implies that it had not been occurring since the beginning. There are quite a number of conversions mentioned between Acts 2 and Acts 10. The conversion of the Samaritans is given in a fair amount of detail. "But when they believed Philip as he preached the things concerning the kingdom of God and the name of Jesus Christ, both men and women were baptized. Then Simon himself also believed; and when he was baptized he continued with Philip, and was amazed, seeing the miracles and signs which were done. Now when the apostles who were at Jerusalem heard that Samaria had received the word of God, they sent Peter and John to them, who, when they had come down, prayed for them that they might receive the Holy Spirit. For as yet He had fallen upon none of them. They had only been baptized in the name of the Lord Jesus. Then they laid hands on them, and they received the Holy Spirit" (Acts 8:12-17). Yet, the experience of the Samaritans is different from Cornelius. The Samaritans were baptized, but they did not receive the gifts of the Spirit immediately. Even though Philip was present, and he had the gifts of the Spirit, these people had to wait until apostles came from Jerusalem. The Spirit was then given to the Samaritans by the laying on of the apostles' hands (Acts 8:18). We must, therefore, conclude that the receiving of the gifts of the Spirit by the hands of the apostles was not the baptism in the Spirit. Otherwise, Peter would have been reminded of more recent baptisms in the Spirit. Instead, he reached all the way back to the beginning of the church. In addition, since baptism in water came before receiving the Spirit in Acts 8 and it came after receiving the Spirit in Acts 10, we must conclude that the receiving of the Spirit in these two came for separate, unrelated purposes.
See: Cornelius Received the Holy Spirit for greater details.
When the Spirit came in these two events the apostles and the household of Cornelius spoke in other languages. "And how is it that we hear, each in our own language in which we were born?" (Acts 2:8). They did not babble; Peter and the apostles preached a lesson that touched people's hearts. "But Peter, standing up with the eleven, lifted up his voice, and said unto them, ..." (Acts 2:14). Later, Paul point out that without communication, speaking in a different language was useless.
"So likewise you, unless you utter by the tongue words easy to understand, how will it be known what is spoken? For you will be speaking into the air. There are, it may be, so many kinds of languages in the world, and none of them is without significance. Therefore, if I do not know the meaning of the language, I shall be a foreigner to him who speaks, and he who speaks will be a foreigner to me" (I Corinthians 14:9-11).
In fact useless (vain or idle) babbling was specifically condemned. "O Timothy! Guard what was committed to your trust, avoiding the profane and idle babblings and contradictions of what is falsely called knowledge -- by professing it some have strayed concerning the faith" (I Timothy 6:20-21). "But shun profane and idle babblings, for they will increase to more ungodliness" (II Timothy 2:16). In these two passages Paul is calling false teaching empty words that have no meaning. If actual communication is called idle babbling, then what do we call a stream of sound that communicates nothing to the listeners?
In a very interesting article that appeared in my local paper, I found this quote, "After the service, Farone placed his right hand on his forehead and began to speak again. This time, the words were impossible to understand, streaming out in a long, rambling string of sound. He had just spoken in tongues, he said later. "This is our power," he added, acknowledging he was unsure of what he had just said." [Sarah Parvini, "Pentecostals speak in tongues less and less," Omaha World-Herald, 9/7/2013].
You'll find nothing like "slain in the Spirit" in the New Testament. The closest you find are unclean spirits (demons) causing people to fall and lose control of themselves. "Then they brought him to Him. And when he saw Him, immediately the spirit convulsed him, and he fell on the ground and wallowed, foaming at the mouth" (Mark 9:20). But this was not the characteristic of the Holy Spirit coming upon people. When people had unclean spirits cast out of them, the distinguishing mark was their calmness. "Then they came to Jesus, and saw the one who had been demon-possessed and had the legion, sitting and clothed and in his right mind" (Mark 5:15).
Why do people babble, shake and fall down and then claim it was by God's power? Because they were told to expect it; in fact, pressure is placed on people to want to act this way because they are told they are not full Christians until they manifest the Spirit. Instead of looking to see what God said about the matter, they get wrapped up in emotions and think that losing control is somehow giving glory to God. "Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven. Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?' And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!'" (Matthew 7:21-23).