Note 1 at Acts 19:1: These twelve men (v. 7) were born again (see note 2 at Jn. 3:3, p. 92 and note 5 at Jn. 3:7, p. 94), otherwise they would not have been called disciples (see note 8 at Jn. 8:31, p. 291). It was certain that they were not the Pharisee's disciples or anyone else's disciples except the disciples of Jesus, otherwise Paul would not have asked them if they had received the Holy Ghost since they had believed. He would have know that no one can receive the baptism of the Holy Ghost until they have first believed on Jesus (see note 27 at Jn. 14:17, p. 491).

Therefore, these men had believed (v. 2) in Jesus but they were not operating in the power of the Spirit that came through the baptism of the Holy Spirit v. 2; see note 1 at Acts 18:24, p. ???). This shows that Christians can be born again without having the baptism of the Holy Spirit. The baptism of the Holy Spirit is a separate experience from being born again (see note 6 at Acts 2:4, p. 576).

When they heard of the Spirit baptism, they believed, they were re-baptized in water in the name of the Lord Jesus (v. 5), then they immediately received the baptism of the Holy Ghost with gifts of the Holy Spirit evident (v. 6). This proves that there does not have to be a waiting period or tarrying for the Holy Ghost (see note 4 at Lk. 24:49, p. 555).