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) 5:1
sa2 5:1THE TRIBES ANOINT DAVID KING OVER ISRAEL. (Sa2 5:1-5)
Then came all the tribes of Israel--a combined deputation of the leading authorities in every tribe. [See on Ch1 11:1.] David possessed the first and indispensable qualification for the throne; namely, that of being an Israelite (Deu 17:15). Of his military talent he had furnished ample proof. And the people's desire for his assumption of the government of Israel was further increased by their knowledge of the will and purpose of God, as declared by Samuel (Sa1 16:11-13).
2 Kings (2 Samuel) 5:3
sa2 5:3King David made a league with them in Hebron before the Lord--(see on Sa1 10:17). This formal declaration of the constitution was chiefly made at the commencement of a new dynasty, or at the restoration of the royal family after a usurpation (Kg2 11:17), though circumstances sometimes led to its being renewed on the accession of any new sovereign (Kg1 12:4). It seems to have been accompanied by religious solemnities.
2 Kings (2 Samuel) 5:6
sa2 5:6HE TAKES ZION FROM THE JEBUSITES. (Sa2 5:6-12)
the king and his men went to Jerusalem unto the Jebusites--The first expedition of David, as king of the whole country, was directed against this place, which had hitherto remained in the hands of the natives. It was strongly fortified and deemed so impregnable that the blind and lame were sent to man the battlements, in derisive mockery of the Hebrew king's attack, and to shout, "David cannot come in hither." To understand the full meaning and force of this insulting taunt, it is necessary to bear in mind the depth and steepness of the valley of Gihon, and the lofty walls of the ancient Canaanitish fortress.
2 Kings (2 Samuel) 5:7
sa2 5:7the stronghold of Zion--Whether Zion be the southwestern hill commonly so-called, or the peak now level on the north of the temple mount, it is the towering height which catches the eye from every quarter--"the hill fort," "the rocky hold" of Jerusalem.
2 Kings (2 Samuel) 5:8
sa2 5:8Whosoever getteth up to the gutter--This is thought by some to mean a subterranean passage; by others a spout through which water was poured upon the fire which the besiegers often applied to the woodwork at the gateways, and by the projections of which a skilful climber might make his ascent good; a third class render the words, "whosoever dasheth them against the precipice" (Ch1 11:6).
2 Kings (2 Samuel) 5:9
sa2 5:9David dwelt in the fort, &c.--Having taken it by storm, he changed its name to "the city of David," to signify the importance of the conquest, and to perpetuate the memory of the event.
David built round about from Millo and inward--probably a row of stone bastions placed on the northern side of Mount Zion, and built by David to secure himself on that side from the Jebusites, who still lived in the lower part of the city. The house of Millo was perhaps the principal corner tower of that fortified wall.
2 Kings (2 Samuel) 5:11
sa2 5:11Hiram . . . sent carpenters, and masons--The influx of Tyrian architects and mechanics affords a clear evidence of the low state to which, through the disorders of long-continued war, the better class of artisans had declined in Israel.
2 Kings (2 Samuel) 5:13
sa2 5:13ELEVEN SONS BORN TO HIM. (Sa2 5:13-16)
David took him more concubines and wives--In this conduct David transgressed an express law, which forbade the king of Israel to multiply wives unto himself (Deu 17:17).
2 Kings (2 Samuel) 5:17
sa2 5:17HE SMITES THE PHILISTINES. (Sa2 5:17-25)
when the Philistines heard that they had anointed David king over Israel--During the civil war between the house of Saul and David, those restless neighbors had remained quiet spectators of the contest. But now, jealous of David, they resolved to attack him before his government was fully established.
2 Kings (2 Samuel) 5:18
sa2 5:18valley of Rephaim--that is, "of giants," a broad and fertile plain, which descends gradually from the central mountains towards the northwest. It was the route by which they marched against Jerusalem. The "hold" to which David went down "was some fortified place where he might oppose the progress of the invaders," and where he signally defeated them.
2 Kings (2 Samuel) 5:21
sa2 5:21there they left their images--probably their "lares" or household deities, which they had brought into the field to fight for them. They were burnt as ordained by law (Deu 7:5).
2 Kings (2 Samuel) 5:22
sa2 5:22the Philistines came up yet again--The next year they renewed their hostile attempt with a larger force, but God manifestly interposed in David's favor.
2 Kings (2 Samuel) 5:24
sa2 5:24the sound of a going in the tops of the mulberry trees--now generally thought not to be mulberry trees, but some other tree, most probably the poplar, which delights in moist situations, and the leaves of which are rustled by the slightest movement of the air [ROYLE].