¹⁴ Now when the apostles who were at Jerusalem heard that Samaria had received the word of God, they sent Peter and John to them, ¹⁵ 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. (Act 8:14-16)
 
Is the Holy Spirit received at salvation? Normally yes.  God the Holy Spirit baptizes, regenerates, indwells, gives a spiritual gift(s) and begins the sanctification process at the moment of salvation – faith in Christ.   However, Acts is a book of transition and is descriptive in nature rather than prescriptive (it describes what happened rather than declares what will happen). In this instance, the people received the Word of God and were baptized in the name of Jesus, but they did not receive the baptism of the Holy Spirit.  Why?

Remember that Jesus in Acts 1:8 told the disciples that they would be “witnesses to Me in Jerusalem, and in all Judea and Samaria and to the end of the earth.”  In Acts 1-7 the gospel was proclaimed in Jerusalem, but it took the persecution against the church to send the gospel scattered throughout Judea and Samaria (Acts 8:1-2).  Saul (later Paul) made havoc of the church, but godly men like Philip went down to the city of Samaria preaching Christ (Acts 8:3-5).  Yet, Philip was not one of the disciples directly commissioned by Jesus.

Consider several things.  First, when Peter and John were sent, they took the authority directly given to them by Jesus to Samaria in fulfillment of Acts 1:8 and confirmed Philip’s ministry among the Samaritans. Second, Peter and John would authenticate God’s ministry through them and prevent a schism between the Jews and Samaritans. Consider that when Jesus was returning to Jerusalem and He passed through Samaria, the Samaritans did not receive Him (Luke 9:52-53). So when Peter and John prayed the Samaritans would receive the Holy Spirit, it was far different than when John wanted to call down fire on them (Luke 9:54). And thirdly, Jesus had given the keys of heaven to Peter (Matt. 16:13-20). Peter opened the doors to the Jews in Jerusalem (Acts 2).  Here he opens the door to the Samaritans (Acts 8).  Peter will open the door to the Gentiles with Cornelius in Acts 10.   

There are challenges to the timing of the Holy Spirit.  In Acts 10:44-48, the Holy Spirit came on Gentiles before they were baptized. The text says there also, that they were baptized in the name of the Lord (Acts 10:48).   Yet, in Acts 19:5, Paul met some disciples from Ephesus who had been baptized into John’s baptism.  When Paul explained the gospel and when they heard the message, Paul baptized them in the name of the Lord Jesus.  Then when Paul laid hands on them, the Holy Spirit came upon them (Acts 19:5-6).

So why? God wanted to demonstrate that the line of authority came through the Jewish apostles.  But He also wanted everyone to know the Samaritans were equal with the Jews, because of the oneness they have in Jesus (Gal. 3:28).  God didn’t want there to be two “universal” churches.  There had been too many years of conflict between Jews and Samaritans.  All believers were equal in Christ.  Again Acts 8:16 is descriptive and transitional.  It does not prescribe what must happen.