Acts 8:30

And Philip ran thither to him
Being very ready to obey the divine order, and hoping he might be an instrument of doing some good, which might issue in the glory of God, and the welfare of men:

and heard him read the prophet Esaias;
that is, "the Book of Isaiah the Prophet"; as before; and so the Ethiopic and Arabic versions read here, as there: he read it out, with a clear and distinct voice, so that Philip could hear him; and this he did, partly through reverence to the word of God, and partly to fix his attention to it the more, that he might the better understand and remember it, and also for delight and pleasure: it is very likely, that it was the Book of Isaiah in the Hebrew tongue in which he was reading, and which language he might understand, though he might be at a loss about the sense of the prophet:

and said, understandest thou what thou readest?
meaning not the language, but the sense; for overhearing him, he perceived it was a prophecy in Isaiah he was reading; which was not so easy to be understood as laws and precepts are, which command this, and forbid that; whereas prophecies were more abstruse, and regarded things to come.