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
1 Chronicles 18:1
ch1 18:1DAVID SUBDUES THE PHILISTINES AND MOABITES. (Ch1 18:1-2)
David . . . took Gath and her towns--The full extent of David's conquests in the Philistine territory is here distinctly stated, whereas in the parallel passage (Sa2 8:1) it was only described in a general way. Gath was the "Metheg-ammah," or "arm-bridle," as it is there called--either from its supremacy as the capital over the other Philistine towns, or because, in the capture of that important place and its dependencies, he obtained the complete control of his restless neighbors.
1 Chronicles 18:2
ch1 18:2he smote Moab--The terrible severities by which David's conquest of that people was marked, and the probable reason of their being subjected to such a dreadful retribution, are narrated (Sa2 8:2).
the Moabites . . . brought gifts--that is, became tributary to Israel.
1 Chronicles 18:3
ch1 18:3DAVID SMITES HADADEZER AND THE SYRIANS. (Ch1 18:3-17)
Hadarezer--or, "Hadadezer" (Sa2 8:3), which was probably the original form of the name, was derived from Hadad, a Syrian deity. It seems to have become the official and hereditary title of the rulers of that kingdom.
Zobah--Its situation is determined by the words "unto" or "towards Hamath," a little to the northeast of Damascus, and is supposed by some to be the same place as in earlier times was called Hobah (Gen 14:15). Previous to the rise of Damascus, Zobah was the capital of the kingdom which held supremacy among the petty states of Syria.
as he went to stablish his dominion by the river Euphrates--Some refer this to David, who was seeking to extend his possessions in one direction towards a point bordering on the Euphrates, in accordance with the promise (Gen 15:18; Num 24:17). But others are of opinion that, as David's name is mentioned (Ch1 18:4), this reference is most applicable to Hadadezer.
1 Chronicles 18:4
ch1 18:4And David took from him a thousand chariots--(See on Sa2 8:3-14). In Sa2 8:4 David is said to have taken seven hundred horsemen, whereas here it is said that he took seven thousand. This great discrepancy in the text of the two narratives seems to have originated with a transcriber in confounding the two Hebrew letters which indicate the numbers, and in neglecting to mark or obscure the points over one of them. We have no means of ascertaining whether seven hundred or seven thousand be the more correct. Probably the former should be adopted [DAVIDSON'S HERMENUTICS].
but reserved of them an hundred chariots--probably to grace a triumphal procession on his return to Jerusalem, and after using them in that way, destroy them like the rest.
1 Chronicles 18:8
ch1 18:8from Tibhath and from Chun--These places are called Betah and Berothai (Sa2 8:8). Perhaps the one might be the Jewish, the other the Syrian, name of these towns. Neither their situation nor the connection between them is known. The Arabic version makes them to be Emesa (now Hems) and Baal-bek, both of which agree very well with the relative position of Zobah.
1 Chronicles 18:9
ch1 18:9Tou--or Toi--whose dominions border on those of Hadadezer. (See on Sa2 8:9-12; Kg1 11:15).
1 Chronicles 18:17
ch1 18:17the Cherethites and the Pelethites--who formed the royal bodyguard. The Cherethites were, most probably, those brave men who all along accompanied David while among the Philistines, and from that people derived their name (Sa1 30:14; Eze 25:16; Zep 2:5) as well as their skill in archery--while the Pelethites were those who joined him at Ziklag, took their name from Pelet, the chief man in the company (Ch1 12:3), and, being Benjamites, were expert in the use of the sling.