A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
2 Kings (2 Samuel) 15:1
sa2 15:1ABSALOM STEALS THE HEARTS OF ISRAEL. (Sa2 15:1-9)
Absalom prepared him chariots and horses, and fifty men to run before him--This was assuming the state and equipage of a prince. The royal guards, called runners, avant couriers, amounted to fifty (Kg1 1:5). The chariot, as the Hebrew indicates, was of a magnificent style; and the horses, a novelty among the Hebrew people, only introduced in that age as an appendage of royalty (Psa 32:9; Psa 66:12), formed a splendid retinue, which would make him "the observed of all observers."
2 Kings (2 Samuel) 15:2
sa2 15:2Absalom rose up early, and stood beside the way of the gate--Public business in the East is always transacted early in the morning--the kings sitting an hour or more to hear causes or receive petitions, in a court held anciently, and in many places still, in the open air at the city gateway; so that, as those whose circumstances led them to wait on King David required to be in attendance on his morning levees, Absalom had to rise up early and stand beside the way of the gate. Through the growing infirmities of age, or the occupation of his government with foreign wars, many private causes had long lain undecided, and a deep feeling of discontent prevailed among the people. This dissatisfaction was artfully fomented by Absalom, who addressed himself to the various suitors; and after briefly hearing their tale, he gratified everyone with a favorable opinion of his case. Studiously concealing his ambitious designs, he expressed a wish to be invested with official power, only that he might accelerate the course of justice and advance the public interests. His professions had an air of extraordinary generosity and disinterestedness, which, together with his fawning arts in lavishing civilities on all, made him a popular favorite. Thus, by forcing a contrast between his own display of public spirit and the dilatory proceedings of the court, he created a growing disgust with his father's government, as weak, careless, or corrupt, and seduced the affections of the multitude, who neither penetrated the motive nor foresaw the tendency of his conduct.
2 Kings (2 Samuel) 15:7
sa2 15:7after forty years--It is generally admitted that an error has here crept into the text, and that instead of "forty," we should read with the Syriac and Arabic versions, and JOSEPHUS, "four years"--that is, after Absalom's return to Jerusalem, and his beginning to practice the base arts of gaining popularity.
my vow, which I have vowed unto the Lord--during his exile in Geshur. The purport of it was, that whenever God's providence should pave the way for his re-establishment in Jerusalem, he would offer a sacrifice of thanksgiving. Hebron was the spot selected for the performance of this vow, ostensibly as being his native place (Sa2 3:3), and a famous high place, where sacrifices were frequently offered before the temple was built; but really as being in many respects the most suitable for the commencement of his rebellious enterprise. David, who always encouraged piety and desired to see religious engagements punctually performed, gave his consent and his blessing.
2 Kings (2 Samuel) 15:10
sa2 15:10HE FORMS A CONSPIRACY. (Sa2 15:10-12)
Absalom sent spies throughout all the tribes of Israel--These emissaries were to sound the inclination of the people, to further the interests of Absalom, and exhort all the adherents of his party to be in readiness to join his standard as soon as they should hear that he had been proclaimed king. As the summons was to be made by the sound of trumpets, it is probable that care had been taken to have trumpeters stationed on the heights, and at convenient stations--a mode of announcement that would soon spread the news over all the country of his inauguration to the throne.
2 Kings (2 Samuel) 15:11
sa2 15:11with Absalom went two hundred men . . . that were called--From their quality, reputation, and high standing, such as would create the impression that the king patronized the movement and, being aged and infirm, was willing to adopt his oldest and noblest son to divide with him the cares and honors of government.
2 Kings (2 Samuel) 15:12
sa2 15:12Absalom sent for Ahithophel--who he knew was ready to join the revolt, through disgust and revenge, as Jewish writers assert, at David's conduct towards Bath-sheba, who was his granddaughter.
the conspiracy was strong--The rapid accession of one place after another in all parts of the kingdom to the party of the insurgents, shows that deep and general dissatisfaction existed at this time against the person and government of David. The remnant of Saul's partisans, the unhappy affair of Bath-sheba, the overbearing insolence and crimes of Joab, negligence and obstruction in the administration of justice--these were some of the principal causes that contributed to the success of this widespread insurrection.
2 Kings (2 Samuel) 15:14
sa2 15:14DAVID FLEES FROM JERUSALEM. (2Sa. 15:13-37)
David said . . . Arise, and let us flee--David, anxious for the preservation of the city which he had beautified, and hopeful of a greater support throughout the country, wisely resolved on leaving Jerusalem.
2 Kings (2 Samuel) 15:18
sa2 15:18all the Gittites, six hundred men--These were a body of foreign guards, natives of Gath, whom David, when in the country of the Philistines, had enlisted in his service, and kept around his person. Addressing their commander, Ittai, he made a searching trial of their fidelity in bidding them (Sa2 15:19) abide with the new king.
2 Kings (2 Samuel) 15:23
sa2 15:23the brook Kidron--a winter torrent that flows through the valley between the city and the eastern side of the Mount of Olives.
2 Kings (2 Samuel) 15:24
sa2 15:24Zadok also, and all the Levites . . ., bearing the ark--Knowing the strong religious feelings of the aged king, they brought it to accompany him in his distress. But as he could not doubt that both the ark and their sacred office would exempt them from the attacks of the rebels, he sent them back with it--not only that they might not be exposed to the perils of uncertain wandering, for he seems to place more confidence in the symbol of the divine presence than in God Himself--but that, by remaining in Jerusalem, they might render him greater service by watching the enemy's movements.
2 Kings (2 Samuel) 15:30
sa2 15:30David went up by the ascent of mount Olivet--The same pathway over that mount has been followed ever since that memorable day.
had his head covered--with a mourning wrapper. The humility and resignation of David marked strongly his sanctified spirit, induced by contrition for his transgressions. He had fallen, but it was the fall of the upright; and he rose again, submitting himself meekly in the meantime to the will of God [CHALMERS].
2 Kings (2 Samuel) 15:31
sa2 15:31David said, Turn, O Lord, . . . the counsel of Ahithophel--this senator being the mainstay of the conspiracy.
2 Kings (2 Samuel) 15:32
sa2 15:32when David was come to the top of the mount, where he worshipped--looking towards Jerusalem, where were the ark and tabernacle.
Hushai the Archite--A native of Archi, on the frontiers of Benjamin and Ephraim (Jos 16:2). Comparing the prayer against Ahithophel with the counsel to Hushai, we see how strongly a spirit of fervent piety was combined in his character with the devices of an active and far-seeing policy.