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) 17:1
sa2 17:1AHITHOPHEL'S COUNSEL OVERTHROWN BY HUSHAI. (Sa2 17:1-14)
Moreover Ahithophel said unto Absalom--The recommendation to take prompt and decisive measures before the royalist forces could be collected and arranged, evinced the deep political sagacity of this councillor. The adoption of his advice would have extinguished the cause of David; and it affords a dreadful proof of the extremities to which the heartless prince was, to secure his ambitious objects, prepared to go, that the parricidal counsel "pleased Absalom well, and all the elders of Israel." It was happily overruled, however, by the address of Hushai, who saw the imminent danger to which it would expose the king and the royal cause. He dwelt upon the warlike character and military experience of the old king--represented him and his adherents as mighty men, who would fight with desperation; and who, most probably, secure in some stronghold, would be beyond reach, while the smallest loss of Absalom's men at the outset might be fatal to the success of the conspiracy. But his dexterity was chiefly displayed in that part of his counsel which recommended a general levy throughout the country; and that Absalom should take command of it in person--thereby flattering at once the pride and ambition of the usurper. The bait was caught by the vainglorious and wicked prince.
2 Kings (2 Samuel) 17:12
sa2 17:12we will light upon him as the dew falleth on the ground--No image could have symbolized the sudden onset of an enemy so graphically to an Oriental mind as the silent, irresistible, and rapid descent of this natural moisture on every field and blade of grass.
2 Kings (2 Samuel) 17:13
sa2 17:13all Israel shall bring ropes to that city--In besieging a town, hooks or cranes were often thrown upon the walls or turrets, by which, with ropes attached to them, the besiegers, uniting all their force, pulled down the fortifications in a mass of ruins.
2 Kings (2 Samuel) 17:14
sa2 17:14The counsel of Hushai the Archite is better than the counsel of Ahithophel--The reasons specified being extremely plausible, and expressed in the strong hyperbolical language suited to dazzle an Oriental imagination, the council declared in favor of Hushai's advice; and their resolution was the immediate cause of the discomfiture of the rebellion, although the council itself was only a link in the chain of causation held by the controlling hand of the Lord.
2 Kings (2 Samuel) 17:16
sa2 17:16SECRET INTELLIGENCE SENT TO DAVID. (Sa2 17:15-22)
send quickly, and tell David--Apparently doubting that his advice would be followed, Hushai ordered secret intelligence to be conveyed to David of all that transpired, with an urgent recommendation to cross the Jordan without a moment's delay, lest Ahithophel's address and influence might produce a change on the prince's mind, and an immediate pursuit be determined on.
2 Kings (2 Samuel) 17:17
sa2 17:17by En-rogel--the fuller's well in the neighborhood of Jerusalem, below the junction of the valley of Hinnom with that of Jehoshaphat.
2 Kings (2 Samuel) 17:18
sa2 17:18and came to a man's house in Bahurim, which had a well in his court--The court was that of the house, and the well an empty cistern. All the houses of the better class are furnished with such reservoirs. Nothing could more easily happen than that one of these wells, in consequence of a deficiency of water, should become dry and it would then answer as a place of retreat, such as David's friends found in the man's house at Bahurim. The spreading of a covering over the well's mouth for the drying of corn is a common practice.
2 Kings (2 Samuel) 17:23
sa2 17:23AHITHOPHEL HANGS HIMSELF. (Sa2 17:23-29)
when Ahithophel saw that his counsel was not followed--His vanity was wounded, his pride mortified on finding that his ascendency was gone; but that chagrin was aggravated by other feelings--a painful conviction that through the delay which had been resolved on, the cause of Absalom was lost. Hastening home, therefore, he arranged his private affairs, and knowing that the storm of retributive vengeance would fall chiefly upon him as the instigator and prop of the rebellion, he hanged himself. It may be remarked that the Israelites did not, at that time, refuse the rites of sepulture even to those who died by their own hands. He had an imitator in Judas, who resembled him in his treason, as well as in his infamous end.
2 Kings (2 Samuel) 17:24
sa2 17:24Then David came to Mahanaim--in the high eastern country of Gilead, the seat of Ish-bosheth's government.
Absalom passed over Jordan--It is not said how long an interval elapsed, but there must have been sufficient time to make the intended levy throughout the kingdom.
2 Kings (2 Samuel) 17:25
sa2 17:25Amasa--By the genealogy it appears that this captain stood in the same relation to David as Joab, both being his nephews. Of course, Amasa was Absalom's cousin, and though himself an Israelite, his father was an Ishmaelite (Ch1 2:17).
Nahash--is thought by some to be another name of Jesse, or according to others, the name of Jesse's wife.
2 Kings (2 Samuel) 17:27
sa2 17:27when David was come to Mahanaim--The necessities of the king and his followers were hospitably ministered to by three chiefs, whose generous loyalty is recorded with honor in the sacred narrative.
Shobi--must have been a brother of Hanun. Disapproving, probably, of that young king's outrage upon the Israelite ambassadors, he had been made governor of Ammon by David on the conquest of that country.
Machir--(See Sa2 9:4). Supposed by some to have been a brother of Bath-sheba, and
Barzillai--a wealthy old grandee, whose great age and infirmities made his loyal devotion to the distressed monarch peculiarly affecting. The supplies they brought, which (besides beds for the weary) consisted of the staple produce of their rich lands and pastures, may be classified as follows: eatables--wheat, barley, flour, beans, lentils, sheep, and cheese; drinkables--"honey and butter" or cream, which, being mixed together, form a thin, diluted beverage, light, cool, and refreshing. Being considered a luxurious refreshment (Sol 4:11), the supply of it shows the high respect that was paid to David by his loyal and faithful subjects at Mahanaim.
2 Kings (2 Samuel) 17:29
sa2 17:29in the wilderness--spread out beyond the cultivated tablelands into the steppes of Hauran.