Acts 13:25
And as John fulfilled his course, he said, Whom think ye that I am? I am not he. But, behold, there cometh one after me, whose shoes of his feet I am not worthy to loose. And as John fulfilled his course, he said, Whom think ye that I am? I am not he. But, behold, there cometh one after me, whose shoes of his feet I am not worthy to loose.
The verse belongs to Paul's Sabbath sermon in the synagogue at Antioch in Pisidia, given after the reading of the law and the prophets when Paul was invited to give a word of exhortation and stood up to address men of Israel and those that fear God. In the sermon around the verse Paul traced how the Lord had dealt with the Jews from deliverance from Egyptian bondage, told how a Saviour had been promised from the seed of David, and preached Jesus as the Saviour of men and the Messiah foretold in prophecy.
As John fulfilled his course means John was completing his appointed work and ministry. John made clear that he himself was not the Messiah or the promised Saviour. He pointed to the one coming after him, Jesus, as far greater in standing, declaring himself unworthy even to perform the lowly task of loosening or unfastening his shoes or sandals. His testimony in the verse thus identifies Jesus as the promised Savior and Messiah.
The passage including the verse teaches that the Lord will not encourage false theories and a low standard, but requires God's people to seek the Lord most earnestly, study the light given in Acts, and humble their hearts before God. This humbling is so the Holy Spirit can refine, enlighten, sanctify and purify them and uphold a higher moral standard in every line of work.