What happened when Peter and John laid hands on the Samaritan believers?

The Samaritan believers received the Holy Spirit after the apostles laid hands on them. Peter and John had been sent from Jerusalem, prayed for them, and then laid hands on them; the Spirit had not yet fallen on any, though they had been baptized in the name of the Lord Jesus.

Les explains that the Jerusalem apostles heard Samaria had received the Word of God, so they sent Peter and John. James was probably already dead, which is why he was not with them. They prayed for the Samaritan believers to receive the Holy Spirit. As yet, in spite of Philip's success in preaching, the Spirit had fallen on none of them; they had only been baptized in the name of the Lord Jesus. Les notes God has His reasons for this. When Peter and John laid hands on them, they received the Holy Spirit, which Les calls amazing.

Acts 8:17

Then laid they their hands on them, and they received the Holy Ghost.

How did the Samaritans in Acts 8 receive the Holy Spirit?

The Samaritan believers received the Holy Spirit when the apostles Peter and John came down from Jerusalem, prayed for them, and laid their hands on them. They had already been baptized in the name of the Lord Jesus, but the Spirit had not yet fallen on any of them.