25 So, when they had solemnly testified and spoken the word of the Lord, they started back to Jerusalem, and were preaching the gospel to many villages of the Samaritans. 26 But an angel of the Lord spoke to Philip saying, “Get up and go south to the road that descends from Jerusalem to Gaza.” ([h]This is a desert road.) 27 So he got up and went; and there was an Ethiopian eunuch, a court official of Candace, queen of the Ethiopians, who was in charge of all her treasure; and he had come to Jerusalem to worship, 28 and he was returning and sitting in his [i]chariot, and was reading the prophet Isaiah. 29 Then the Spirit said to Philip, “Go up and join this [j]chariot.” 30 Philip ran up and heard him reading Isaiah the prophet, and said, “Do you understand what you are reading?” 31 And he said, “Well, how could I, unless someone guides me?” And he invited Philip to come up and sit with him. 32 Now the passage of Scripture which he was reading was this:

“He was led as a sheep to slaughter;
And as a lamb before its shearer is silent,
So He does not open His mouth.
33 “In humiliation His judgment was taken away;
Who will [
k]relate His [l]generation?
For His life is removed from the earth.”

34 The eunuch answered Philip and said, “Please tell me, of whom does the prophet say this? Of himself or of someone else?” 35 Then Philip opened his mouth, and beginning from this Scripture he preached Jesus to him. 36 As they went along the road they came to some water; and the eunuch *said, “Look! Water! What prevents me from being baptized?” 37 []And Philip said, “If you believe with all your heart, you may.” And he answered and said, “I believe that Jesus Christ is the Son of God.”] 38 And he ordered the [n]chariot to stop; and they both went down into the water, Philip as well as the eunuch, and he baptized him. 39 When they came up out of the water, the Spirit of the Lord snatched Philip away; and the eunuch no longer saw him, but went on his way rejoicing (Acts8:25-39). 

A part of the reason for my going through these sermons and exchanges in Acts is to demonstrate that the apostles’ audience and the first converts to the Christian faith were either Jewish, Samaritan (being effectively a sect of Jews who also worshipped YHWE and observed the Law of Moses) or as in the case of the Ethiopian eunuch, a Jewish proselyte. That is evidenced from the fact that he had been on pilgrimage to the Jewish temple and was reading the Old Testament. It is to affirm a major thesis within the Little Book of Providence (not to mention Paul’s 11th chapter to the Romans) that what we know of as Christian salvation was not envisaged for the Gentile nations in the current age but resulted from the rejection of the Jewish nation as sole inheritors of the Kingdom. My Book considers the associated providential and dispensational (millennial) implications of this phenomenon. These have largely been eluded because such cannot currently  be reconciled with some of the narrow, dualistic  Augustinian derived theological assumptions the Church has relied upon for so long,

The other reason for this process is to demonstrate what the very earliest (and purest) evangelism looked like in terms of what potential converts to the Faith were required to do or believe. This narrative serves that purpose well in which it is to be observed that the Ethiopian having  been instructed by Philip concerning Jesus (in this case using only data available from the Old Testament – so forget the counter-intuitive intricacies of Pauline justification and the like), he came across water and requested to be baptized. The subsequent dialogue provides all we need to know: “If you believe with all your heart, you may.” And he answered and said, “I believe that Jesus Christ is the Son of God.” And he ordered the chariot to stop; and they both went down into the water, Philip as well as the eunuch, and he baptized him”. Truly, the unnamed Ethiopian was now a Christian. If he were still alive in a few decades time he would have the opportunity to further inform and deepen his faith through the teaching of the apostles in their pastoral letters to the churches. But in the meantime he possessed sufficient knowledge to believe in his heart that Jesus Christ was the Son of God and receive baptism for the remission of his sins, the Spirit also being given to those who obey God. That, as Acts should affirm to all readers, pertains to the essentials of what makes and defines the Christian.