The above question was asked this last week by e-mail by a person trying to prove that baptism is not essential to salvation. The man reasoned that since the Holy Spirit came upon Cornelius and his household before they were baptized, then Cornelius was saved before he was baptized, therefore making baptism non-essential to salvation. The man argued that the Holy Spirit came upon no one else except those who were saved, so in his mind Cornelius had to be saved when the Holy Spirit came upon him and his household. This man acknowledged that Peter commanded Cornelius and his household to be baptized, but he insisted that this was just a public acknowledgment that they had accepted Jesus and not for salvation. This of course is the old argument by those who don't want to accept what Jesus said in Mark 16:16, "He that believeth and is baptized shall be saved; but he that believeth not shall be damned "
Yet, we need to ask and find God's answer to the question, was Cornelius saved when the Holy Spirit came upon him? First, we need to understand how the Holy Spirit normally came upon people. In Acts chapter 8, we find that Philip preached to the people of Samara and they believed and were baptized. Later in that chapter Peter and John came down from Jerusalem and we find these words, "Who, when they were come down, prayed for them, that they might receive the Holy Ghost: (For as yet he was fallen upon none of them: only they were baptized in the name of the Lord Jesus.) Then laid they their hands on them, and they received the Holy Ghost" Here was the normal way people received the Holy Spirit in a miraculous way, they became Christians and then the apostles laid hands on them and they received the power to perform miracles as the Holy Spirit gave them that power.
Cornelius and his household were an exception to the normal way people received the Holy Spirit. For the Jewish Christians to accept that God had accepted Gentiles on the same level as the descendants of Abraham would be very difficult without some sign from God. The normal pattern would not have been enough, without some sign from God it would only seem that the Gentiles were being sanctioned by the apostles and not God. By giving the Holy Spirit to the Gentiles directly, without human agency, God proved for all times that the Gentiles are to be offered salvation and that all children of God are equal. In other words, God was proving that the choice was His, not Peter's nor anyone elses'. Here we have the only example of non- Christians delivering a message from God to Christians. What was that message? That God had accepted the Gentiles unto salvation and as Peter stated, "What was I, that l could withstand God?" The Jewish Christians then glorified God for His mercy.