Acts 8:37 - Matthew Poole's English Annotations on the Holy Bible

With all thine heart: a verbal profession is not a sufficient believing, Romans 10:10 though we can discern no other, yet God can, and will not he mocked: Philip, in God's name, requires a faith with all the heart, and not such as Simon Magus had, who is said to believe, and be baptized, Acts 8:13. I believe that Jesus Christ is the Son of God; this was the only thing necessary, either then or now, if rightly understood. The eunuch was instructed concerning God out of the law, and was one of them that waited for his salvation; which here he acknowledgeth to be only found in Christ, whom he owns to be the Messiah, who made his soul an offering for sin, Isaiah 53:10, and did bear our griefs, and carried our sorrows, Isaiah 53:4, and was wounded for our transgressions, Isaiah 53:5; for all these things Philip had told him were meant of our Saviour, which he did believe were so to be understood.