Why does it say that David conquered, and not that he struck?
Radak: He killed in war only until they were conquered. He captured the rest, and took from them redemption of their souls. This is like Targum Yonasan - he tied them in fetters until they redeemed themselves.
Why does it say here 1,700 horsemen, and in Divrei ha'Yamim I, 18:4 it says 1,000 chariots and 7,000 horsemen?
Radak: Here it counts only the great officers in Hadad'ezer's camp.
Malbim: Every chariot had 10 horses, and one horseman was appointed over them. Here it counts the number of such overseers. Therefore it combines the chariots with the horsemen (it does not give the number of chariots). In Divrei ha'Yamim it counts every horse by itself, therefore it counts 1000 chariots by themselves, and 7,000 Parashim, i.e. horses 1 . Also below (10:18, regarding Aram) it says 700 chariots, and in Divrei ha'Yamim I, 19:18 it says 7,000, for the same reason.
I cannot explain his calculation. Divrei ha'Yamim says that there were 1,000 chariots. If it counts all the horses, there should be 10,000! Perhaps the text should say that there were seven horses in each chariot. In addition to the chariots, there were 700 other horsemen; together, they were 1,700. Divrei ha'Yamim does not mention the extra horsemen. Indeed, Aram had 10 horses in each chariot. We find that the number varied. Divrei ha'Yamim 2 1:17 implies that each chariot had four horses! (PF)
What is the meaning of "va'Y'aker David Es Kol ha'Rechev", and why did he do so?
Radak: It is to remove the feet from the knee and below, so the enemy cannot use them for war. One may destroy something only if it damages, or it is Asur b'Hana'ah, or to blot out memory, e.g. of Amalek. Rashi - he could not keep [more than he needed from] them, due to "Lo Yarbeh Lo Susim 1 " (Devarim 17:16).
Radak: The Torah forbids keeping more horses than needed, lest Yisrael regularly go to Egypt, for the [best] horses are there.
Why did David keep 100 chariots?
Rashi: This is what he needed. A chariot has four horses, like it says in Divrei ha'Yamim 2 1:17 that an [Egyptian] chariot sold for 600 silver pieces, and a horse for 150. 1
The cost of the wagon itself is paltry, and is ignored. Perhaps it was given for free, like sellers often give a discount to one who buys a certain quantity. (PF)
