44 While Peter was still saying these things, the Holy Spirit fell on all who heard the word. 45 And the believers from among the circumcised who had come with Peter were amazed, because the gift of the Holy Spirit was poured out even on the Gentiles. 46 For they were hearing them speaking in tongues and extolling God. Then Peter declared, 47 “Can anyone withhold water for baptizing these people, who have received the Holy Spirit just as we have?” 48 And he commanded them to be baptized in the name of Jesus Christ. Then they asked him to remain for some days. (Acts 10:44-48 (ESV)
While Peter is speaking the Holy Spirit falls upon the people as is evidenced by the speaking in tongues through which they extolled God. There is a lot of uncertainty surrounding just what it means to speak in tongues, but what we do know is that it was not unintelligible. Peter and the believers of the circumcised were convinced by it that these people, who were not circumcised had received the Spirit. So Peter comes to the conclusion that they should be baptized. This is the point of the whole story. What is great here is that the people received the Holy Spirit even before baptism, where as in the previous chapters the Samaritans received the Spirit after they had been baptized. In both of these cases the Spirit is used as confirmation of baptism and the validity of the faith for these people.
In fact there are only three cases where the Holy Spirit is given out our poured out on the people in this manner, Pentecost, for the whole church gathered together, in Samaria amongst baptized believers together, and here in Cornelius’s home. Never is it heard of that the Holy Spirit falls upon or is given out to an individual believer apart from his baptism in the New Testament. In the New Testament this is not an experience of the individual, but the experience of the church marking milestones in the direction the church should go when faced with decisive decisions.