Since those who wanted to go on to follow Jesus had to be re-baptized—or baptized into His name—what was the good of John’s baptism? God never asks us to do anything without a good reason. Submission to John did indeed prepare the way of the Lord. Those who allowed the axe to be laid to the root in his baptism were open to the message of the kingdom. They were not blinded by religious tradition or bound by the fear of their elders. They were already aware of their personal need. For this reason, they could welcome a Savior who was also a king—one who would tell them how to live their lives. 

They were familiar with the meaning of water baptism. 

They already knew to expect something to happen in the waters of baptism. This was no mere rite; it was a meeting with God. When they were told to be baptized in the name of the Messiah after the Holy Spirit proved His resurrection and ascension on the day of Pentecost, they obeyed. 

They knew to expect the gift of the Holy Spirit. 

John was always making comparisons between his water baptism and the Baptism in the Holy Spirit. Jesus and His disciples baptized in water, but this was not the emphasis of their ministry. The unique ministry of the Messiah was to pour out the promise of the Father upon those who believed. Those who were immersed in water by John were told to expect the Messiah to immerse them in the Holy Spirit. The axe had been laid to the root in the water, but the Messiah would come and burn all that needed to be purged