Final answer:
Philip the Evangelist witnessed to the Ethiopian servant, explaining the Scriptures to him and subsequently baptizing him, as described in the Acts of the Apostles in the New Testament.
Step-by-step explanation:
The individual who witnessed to the Ethiopian servant is Philip the Evangelist, as described in the Acts of the Apostles in the New Testament. The story can be found in Acts 8:26-40, where Philip, directed by an angel of the Lord, encounters the Ethiopian eunuch, who is a high official under Candace, queen of the Ethiopians, and in charge of all her treasury.
The eunuch was reading the book of Isaiah while traveling in his chariot. Philip explains the Scriptures to him, and, as they travel, they come across some water, prompting the eunuch to ask for baptism. Philip then baptizes him, completing the witness to the Ethiopian.