“Of this man's seed has God according to promise brought to Israel a Saviour, Jesus, when John had first preached before his coming the baptism of repentance to all the people of Israel. And as John was fulfilling his course, he said, ‘What do you suppose that I am? I am not he. But behold, there comes one after me the shoes of whose feet I am not worthy to unloose.”
And of the seed of this paragon among kings has arisen the One Whom Paul is here to announce. For of the seed of David, according to God's promise to Israel (Isaiah 11:1-4), God has brought to Israel a Saviour, Jesus. And as God had borne witness to David (Acts 13:22), so now He has borne witness to Him too, for He sent before Him John the Baptiser proclaiming a baptism of repentance for the forgiveness of sins who had declared concerning Him that he, John, was not worthy even to unloose His sandals (Luke 3:16). And when men had magnified John he had repudiated such magnification saying, ‘who am I? I am not the One.' And had pointed forward to Jesus as the One to be magnified (John 1:19-27).
This detailed mention of John is suggestive. There had been no need to combat the belief in John as ‘the prophet' while in Jerusalem and Judaea, for there they had all witnessed what had followed. John was history. But it was different here, out in the wider world, where news filtered through more slowly. Here in ‘the Dispersion' were many who had been visitors to Jerusalem in past years whose last memory of it was of John's ministry. They had been disturbed by it and had responded to it. Many still lived by it (Acts 18:24-28). They needed to be made aware that the greater than John had come, the One to Whom he had pointed. This authenticates the words of this speech as spoken to people in the Gentile world who would still have remembered and have honoured John without being aware of Jesus (a touch not likely from an inventor). We can compare how John's witness is still seen as having produced powerful speakers going around proclaiming his message (Acts 18:24-28; Acts 19:1-6).
There would be many present who had flocked to hear John when they had gone up to the feasts, for he had preached over a number of years, and they would remember what had been said, and still look back to him with reverence. Thus when Paul spoke of him it would quicken their hearts. (Some few would, of course, actually remember having heard Jesus. But people from these areas would not go up to the feasts every year so that those who had heard Jesus would not be as many as had heard only John).