And Philip ran - Indicating his haste and his desire to obey the suggestions of the Spirit. A thousand difficulties might have been started in the mind of Philip if he had reflected a little. The eunuch was a stranger; he had the appearance of a man of rank; he was engaged in reading; he might be indisposed to be interrupted or to converse, etc. But Philip obeyed without any hesitation the instructions of the Spirit, and "ran" to him. It is well to follow the first suggestions of the Spirit; to yield to the clear indications of duty, and to perform it at once. Especially in a deed of benevolence, and in conversing with others on the subject of religion, our first thoughts are commonly the safest and the best. If we do not follow them, the calculations of avarice, or fear, or of worldly prudence are very apt to come in. We become alarmed; we are afraid of the rich and the great; we suppose that our conversation and admonitions will be unacceptable. We may learn from this case:
(1) To do our duty at once, without hesitation or debate.
(2) we shall often be disappointed in regard to subjects of this kind. We shall find candid, humble, Christian conversation far more acceptable to strangers, to the rich, and to the great, than we commonly suppose. If, as in this case, they are "alone"; if we approach them kindly; if we do not rudely and harshly address them, we shall find most people willing to talk on the subject of religion. I have conversed with some hundreds of persons on the subject of religion, and do not now recollect but two instances in which I was rudely treated, and in which it was not easy to gain a respectful and kind attention to Christian conversation.
And heard him read - He was reading "loud" - sometimes the best way of impressing truth on the mind in our private reading the Scriptures.
And said - This question, there might have been reason to fear, would not be kindly received. But the eunuch's mind was in such a state that he took no offence from such an inquiry, though made by a footman and a stranger. He doubtless recognized him as a brother Jew. It is an important question to ask ourselves when we read the Sacred Scriptures.

Heard him read the Prophet Esaias - The eunuch, it seems, was reading aloud, and apparently in Greek, for that was the common language in Egypt; and, indeed, almost in every place it was understood. And it appears that it was the Greek version of the Septuagint that he was reading, as the quotation below is from that version.

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.

Understandest thou what thou readest?--To one so engaged this would be deemed no rude question, while the eager appearance of the speaker, and the question itself, would indicate a readiness to supply any want of insight that might be felt.

And Philip running to him, said, Understandest thou what thou readest? - He did not begin about the weather, news, or the like. In speaking for God, we may frequently come to the point at once, without circumlocution.