Adam Clarke's Commentary on the Bible

Verse 25 (Acts 13:25)

As John fulfilled his course - As John was fulfilling his race, he said, etc. It has been supposed that the word δρομον , course, or race, is used here to point out the short duration of the Baptist's ministry, and the fervent zeal with which he performed it. It signifies properly his ministry, or life. A man's work, employment, function, etc., is his race, course, or way of life. John had a ministry from God; and he discharged the duties of it with zeal and diligence; bore the fatigues of it with patience and resignation; and was gloriously successful in it, because the hand of the Lord was with him.

- Adam Clarke's Commentary on the Bible