John Gill's Bible Commentary Ver. 7. And when David heard of [it] , etc.] Of the preparation made by the Ammonites to fight with him: he sent Joab and all the host of the mighty men : he sent out Joab his general, and an army under his command, consisting of men of strength, valour, and courage; or all the host and the mighty men, as Kimchi and Ben Melech, the famous mighty men mentioned in ( 2 Samuel 23:8); he did not think it advisable to wait for the Ammonites, but carried the war into their own country, and, instead of suffering them to invade his dominions, he invaded theirs.
Matthew Henry Commentary
Verses 6-14 - They that are at war with the Son of David, not only give the provocation, but begin the war. God has forces to send against thos that set his wrath at defiance, Isa 5:19, which will convince them tha none ever hardened his heart against God, and prospered. Christ' soldiers should strengthen one another's hands in their spiritual warfare. Let nothing be wanting in us, whatever the success be. When we make conscience of doing our duty, we may, with satisfaction, leave the event with God, assuredly hoping for his salvation in his own way an time.
Original Hebrew וישׁמע8085 דוד1732 וישׁלח7971 את853 יואב3097 ואת853 כל3605 הצבא6635 הגברים׃1368