Why did the Holy Spirit manifest with signs in the Book of Acts?
The Holy Spirit manifested with signs in Acts for a divine purpose: to prove God was now working through the Holy Spirit, to show Israel that Gentiles were being saved, and to demonstrate a change in God's program—away from John's baptism and Christ's earthly ministry to the message of the cross, death, burial, and resurrection.
Les explains that whenever the Holy Spirit was manifested in the Book of Acts, it was for a divine purpose—to prove something. It showed Israel that God was now moving in the work of the Holy Spirit. It proved to Jews in the house of the Gentiles that God was now saving Gentiles. It was also manifested in those twelve Jews in Acts 19 to show a change in the overall program: it was no longer based on John's baptism and Christ's earthly ministry, but on that which followed the work of the cross—His death, burial, and resurrection. The three categories were Israel in Acts 2, Gentiles in Cornelius's house in Acts 10, and transitional Jews in Acts 19 who had been saved under John's baptism but knew nothing of Paul's Gospel, the Body of Christ, and further revelations.