Is it this: Acts, Chapter 8:
26 Now an angel of the Lord spoke to Philip, saying: Arise, go towards the south, to the way that goeth down from Jerusalem into Gaza: this is desert. 27 And rising up, he went. And behold a man of Ethiopia, an eunuch, of great authority under Candace the queen of the Ethiopians, who had charge over all her treasures, had come to Jerusalem to adore. 28 And he was returning, sitting in this chariot, and reading Isaias the prophet. 29 And the Spirit said to Philip: Go near, and join thyself to this chariot. 30 And Philip running thither, heard him reading the prophet Isaias. And he said: Thinkest thou that thou understandest what thou readest?
31 Who said: And how can I, unless some man show me? And he desired Philip that he would come up and sit with him. 32 And the place of the scripture which he was reading was this: He was led as a sheep to the slaughter; and like a lamb without voice before his shearer, so openeth he not his mouth. 33 In humility his judgment was taken away. His generation who shall declare, for his life shall be taken from the earth? 34 And the eunuch answering Philip, said: I beseech thee, of whom doth the prophet speak this? of himself, or of some other man? 35 Then Philip, opening his mouth, and beginning at this scripture, preached unto him Jesus.
36 And as they went on their way, they came to a certain water; and the eunuch said: See, here is water: what doth hinder me from being baptized? 37 And Philip said: If thou believest with all thy heart, thou mayest. And he answering, said: I believe that Jesus Christ is the Son of God. 38 And he commanded the chariot to stand still; and they went down into the water, both Philip and the eunuch: and he baptized him. 39 And when they were come up out of the water, the Spirit of the Lord took away Philip; and the eunuch saw him no more. And he went on his way rejoicing. 40 But Philip was found in Azotus; and passing through, he preached the gospel to all the cities, till he came to Caesarea.