John Calvin Commentary Acts 8:35

"And Philip opened his mouth, and beginning from this Scripture, preached unto him Jesus." — Acts 8:35 (ASV)

Philip, opening his mouth. In Scripture, to open the mouth signifies beginning a long speech about some serious and important matter. Therefore, Luke’s meaning is that Philip began to discourse on Christ with full voice, so to speak. He says that Philip began with this prophecy because no other depicts Christ more vividly, and it was then before him.

Therefore, after Philip had shown from the prophet's words how Christ would come and what was to be hoped for from Him, he then connected this to the reality. He did this so that the eunuch might know that the Christ who was promised had already been revealed and given, and so that he might understand His power.

Where it is translated as he preached Christ, Luke says that he preached the gospel. The meaning is that Philip taught what Christ Himself proclaimed in His gospel and commanded to be taught. From this we gather that when Christ is known, we have the sum of the gospel.