Why did the Holy Spirit tell Philip to go to the Ethiopian eunuch's chariot?
The Holy Spirit directed Philip to the chariot because God, in His sovereignty, had an intrinsic interest in this particular individual. Philip was chosen as the human instrument to explain Isaiah 53 and lead the Ethiopian official to a knowledge of salvation, rather than sending an angel or a highly educated person.
Les teaches that God is sovereign and in control of every detail, and He had an intrinsic interest in this situation. The Holy Spirit therefore directed Philip to this particular person. The Ethiopian had been to Jerusalem to worship and was returning in his chariot, reading Isaiah the prophet—specifically Isaiah 53, an appropriate portion for approaching Jews about the finished work of Christ. When Philip asked if he understood, the man replied, 'How can I?' Les maintains that God did not leave His Word to angels or highly educated seminarians, but with the Holy Spirit's leading placed it in the hands of ordinary people. God does not send an angel or a super-educated person to bring someone to salvation; He uses common, ordinary people, and Philip was the human instrument.
Then the Spirit said unto Philip, Go near, and join thyself to this chariot.