Read Acts 8.
The environment went from being hostile toward believers in Jesus to murder and imprisonment. The Sanhedrin appointed a young enthusiast by the name of Saul of Tarsus to lead the persecution (7:58, 9:1-2). The bad news is that Christ followers began leaving Judea, fleeing for their lives. The good news is that they spread the message of Jesus everywhere they went. In Acts 1:8, Jesus foretold that the message would be proclaimed in "Judea and Samaria, and to the end of the earth." Now, Philip, one of the seven selected to serve the church in chapter 6, officially took take the Gospel of Jesus to Samaria.
1. Signs confirmed the message.
This was not exactly virgin territory. Previously, Jesus opened this door of belief at the Samaritan city of Sychar (John 4). But the message of the death, burial and resurrection would have been new to them. Like Stephen, Philip had no Bible, just Old Testament knowledge, a personal salvation, and the empowerment of the Holy Spirit. In this transitional period of time in the book of Acts, God used the miracles of healing and exorcism to confirm the validity of the message preached. The result was that "there was much joy in that city." The believers were baptized as a public demonstration of their personal faith in Jesus (v.12).
2. The Spirit confirmed the ministry.
Other passages in the New Testament confirm that the Holy Spirit indwells the believer in Jesus at the moment of salvation (Romans 8:9). However, here there is an abnormality. Peter and John were sent by the Apostles to confirm the Samaritan ministry. For God's own purposes, the indwelling of the Spirit was delayed in this instance until the Apostles arrived. This happened in Acts 2 in Judea. It occurred here as the church was being established for the first time in Samaria. Another abnormality like this is recorded in Acts 10 as Peter officially took the Gospel to the Gentiles (10:44-45). Step by step the word of God was being spread.
3. Baptism confirmed personal belief.
Next, Philip had a divine encounter with the treasury official of Ethiopia. As a man of wealth, he possessed his own copy of at least Isaiah. As a foreigner and a eunuch, he would have been denied access to full worship at the Temple. But, despite this and his pagan culture, he had traveled to Jerusalem in order worship God. As Philip explained Isaiah's message and told of Jesus, either he mentioned baptism or the eunuch knew of it. His question and Philip's answer is clear. Christian baptism is only for those personally believe in Jesus as Savior. There is no power in the water. Without personal faith, there is no meaning. Being lowered into the water pictures a death to the old self. Being brought up out of the water pictures being raised to a new life in Christ. It is what the Holy Spirit has already done on the inside of the believer. (Romans 6:4)