Acts 13:25

And as John fulfilled his course
Or race, the work of the ministry he was called to; as he was preaching and baptizing, which were the race set before him to run, and in which he ran well; he made full proof of his ministry. The life of every Christian is a race, and especially of a minister of the Gospel, and which requires strength, courage, agility, patience, and perseverance; this world is the place in which they run; and this is only the running time; in heaven they will sit down on the throne with Christ; the way in which they run, is the way of their duty, the way of God's commandments; the mark they have in view, which they keep their eye on, and to which they direct their course, is Christ; and glory is the incorruptible crown they run for, and which, when they have finished their course, will be given them by the chief shepherd and righteous judge; see ( 2 Timothy 4:7 2 Timothy 4:8 ) and this is to be understood, not of the end of John's race, or ministry, but rather of the beginning of it; for it was then, he said,

whom think ye that I am? I am not he;
that is the Messiah. The apostle seems to refer to ( John 1:19 John 1:20 ) when the Jews asked him who he was, and he freely declared he was not the Christ; there the question is put by them to him, here by him to them; doubtless the questions were put by both; however the sense is the same, that he was not the Messiah, but he bore testimony to him that was:

but behold there cometh one after me;
meaning Jesus, who was the Messiah, and who when John spoke these words, was coming after him from Galilee to Jordan to be baptized by him, and who in a little while after that came forth in the public ministry of the word: John was to come forth first, and then Jesus after him, because he was the harbinger of the Messiah, whose coming he was to proclaim and prepare men for, and whose person he was to point out; for though he is said to be after him, he was not in any sense inferior to him: John was born into the world before Christ, as man, was born, yet he as the eternal Son of God was before John, was from the beginning, even from eternity; John entered on the office of his ministry before him, but Christ was not below him; as not in the dignity of his person, so neither in the nature and excellency of his office; and John takes care to secure the honour and glory of Christ, and to prevent any low opinion that might be entertained of him from what he had said, by adding,

whose shoes of his feet I am not worthy to loose;
suggesting hereby, that he was unworthy to be his servant, to perform the meanest part of service for him that could be thought of; so far was he from assuming any preference to him on account of his being before him, as his forerunner; see ( Matthew 3:11 ) ( John 1:27 ) . (See Gill on Matthew 3:11). (See Gill on John 1:27).