And Philip ran thither to him, and heard him read the prophet Esaias, and said, Understandest thou what thou readest?

People's New Testament

8:29,30 The Spirit said. How we are not told. Philip promptly obeyed, ran to the chariot, listened and heard what he read, and then asked his question, the result of which was that he was asked to take his place in the chariot to explain the Scripture.

Wesley's Notes

8:30 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.

Jamieson-Fausset-Brown Bible Commentary

30. 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.

Matthew Henry's Concise Commentary

8:26-40 Philip was directed to go to a desert. Sometimes God opens a door of opportunity to his ministers in very unlikely places. We should study to do good to those we come into company with by travelling. We should not be so shy of all strangers as some affect to be. As to those of whom we know nothing else, we know this, that they have souls. It is wisdom for men of business to redeem time for holy duties; to fill up every minute with something which will turn to a good account. In reading the word of God, we should often pause, to inquire of whom and of what the sacred writers spake; but especially our thoughts should be employed about the Redeemer. The Ethiopian was convinced by the teaching of the Holy Spirit, of the exact fulfilment of the Scripture, was made to understand the nature of the Messiah's kingdom and salvation, and desired to be numbered among the disciples of Christ. Those who seek the truth, and employ their time in searching the Scriptures, will be sure to reap advantages. The avowal of the Ethiopian must be understood as expressing simple reliance on Christ for salvation, and unreserved devotion to Him. Let us not be satisfied till we get faith, as the Ethiopian did, by diligent study of the Holy Scriptures, and the teaching of the Spirit of God; let us not be satisfied till we get it fixed as a principle in our hearts. As soon as he was baptized, the Spirit of God took Philip from him, so that he saw him no more; but this tended to confirm his faith. When the inquirer after salvation becomes acquainted with Jesus and his gospel, he will go on his way rejoicing, and will fill up his station in society, and discharge his duties, from other motives, and in another manner than heretofore. Though baptized in the name of the Father, Son, and Holy Ghost, with water, it is not enough without the baptism of the Holy Ghost. Lord, grant this to every one of us; then shall we go on our way rejoicing.