Adam Clarke on Judges 1:21

The Jebusites dwell with the children of Benjamin - Jerusalem was situated partly in the tribe of Judah, and partly in the tribe of Benjamin, the northern part belonging to the latter tribe, the southern to the former. The Jebusites had their strongest position in the part that belonged to Benjamin, and from this place they were not wholly expelled till the days of David. See the notes on Jdg 1:8. What is said here of Benjamin is said of Judah, Jos 15:63. There must be an interchange of the names in one or other of these places.

Unto this day - As the Jebusites dwelt in Jerusalem till the days of David, by whom they were driven out, and the author of the book of Judges states them to have been in possession of Jerusalem when he wrote; therefore this book was written before the reign of David.