‘But an angel of the Lord spoke to Philip, saying, “Arise, and go toward the south to the way which goes down from Jerusalem to Gaza. The same is desert.'
The ‘angel of the Lord' tells Philip that he must rise and go south towards ancient Gaza, a city slightly inland which, in contrast with new port of Gaza, was mainly in ruins. It was on the road from Jerusalem to Egypt. And on the way which led there, in a place where the land tended to be deserted, he would learn what he must do. The description ‘the bit which is desert' probably indicated a well know place on that road at the time. That the man was to be found there indicated pictorially the thirst that possessed his soul. Or it may mean that the old Gaza was like a desert, ‘Gaza the deserted' (in contrast with ‘maritime Gaza'). Either way there is the hint that the man's soul was needing ‘water' and that his salvation would come from the wilderness, as had the living oracles and Tabernacle of old (Acts 7:38; Acts 7:44-49).
‘An angel of the Lord.' In the Old Testament ‘the angel of the Lord' appears throughout, from Genesis to Zechariah, as representing God Himself in a kind of extended self. The description often indicates the actual appearance of Him in discernible form, but is regularly used of God making a communication with a specific person. Here it may simply be indicating that Philip was so conscious of a presence with him that he thought in such terms, something which went beyond his usual experience of the Holy Spirit.