John Gills Exposition of the Bible Commentary - 2 Samuel 15:8
For thy servant vowed a vow while I abode at Geshur in Syria ,.... When at his grandfather's court there: saying, if the Lord will bring me again indeed to Jerusalem ; which he might be sincerely desirous of: then I will serve the Lord ; but it is a question whether he ever made a vow to this purpose, or concerned himself about serving the Lord; but it rather may be, this was a lie of his, now framed in order to get leave of the king to go to Hebron. read more
Matthew Henry's Complete Commentary - 2 Samuel 15:7-12
We have here the breaking out of Absalom's rebellion, which he had long been contriving. It is said to be after forty years, 2 Sam. 15:7. But whence it is to be dated we are not told; not from David's beginning his reign, for then it would fall in the last year of his life, which is not probable; but either from his first anointing by Samuel seven years before, or rather (I think) from the people's desiring a king, and the first change of the government into a monarchy, which might be about... read more