Who were the Avim, and why does the Torah need to inform us that the Kaftorim conquered them and took over their land?
Rashi: The Avim were a branch of the P'lishtim, 1 which Yisrael could not conquer due to the covenant that Avraham made with Avimelech. So Hashem sent the Kaftorim to take it, thereby enabling Yisrael to capture it from them. 2
Ramban #1: The Avim were Cana'anim, Their land, which was promised to Avraham, was part of Eretz Yisrael [that Yisrael was commanded to conquer], even though the Kaftorim, who were descendents of the Egyptians, 3 conquered them and took over their land.
Ramban #2: The Avim were Chivim, one of the seven nations of Cana'an. Eisav took part of their land, and Kaftorim took the rest. Yisrael may take only the part that Kaftorim took. . 4
Ramban #3 (citing Midrash Rabah): They were actually Refa'im. 5 Mo'av, Eisav and Amon all took parts of Eretz Refa'im, and Yisrael were not permitted to take it from them. What the Kaftorim captured however, was permitted to Yisrael.
Ramban #4 and Rashbam (in Pasuk 20 - both citing Chulin, 60b): They came from Teiman 6 and were so-called either because they desired 7 many gods, or because whoever saw them suffered convulsions ('Ochzaso Avis').
Seforno: The Avim were part of the P'lishtim or of the B'nei Eisav, and their land was forbidden to Yisrael due, either to Hashem's promise or to Avraham's covenant with Avimelech. 8 But now that the Kaftorim conquered it, it became permitted to Yisrael.
Oznayim la'Torah: The Kaftorim were midgets one Amah tall, yet Hashem helped them to defeat the mighty Avim, who placed fear into all who saw them - in the same way as He helped Edom, Mo'av and Amon to defeat the superior Refa'im, Eimim and Zamzumim in order to settle them in their respective lands. 9 And the Torah mentions all this, to allay the fears of Yisrael, who, following the Meraglim's description of the giants, were afraid of Sichon and Og - whom they were about to fight, particularly bearing in mind that, not only Sichon and Og were giants, but so were the all of the Emori nation. 10 And Hashem was now reassuring them that He would do the same for them in order to settle them in their land.
Rashi: Since they are mentioned together with their five princes in Yehoshua, 13:3. The Ramban maintains that, although the Avim are mentioned together with the princes of the P'lishtim, they were a separate nation. See Ramban DH 'Aval Rashi'. However he concludes that these are two opinions in Chulin, 60b, and In the course of his commentary, he appears to waver between the two explanations. Refer to 2:11:2:2*.
In the same way that Yisrael could fight Sichon and take his land, even though it had previously belonged to Mo'av and Amon, which was forbidden to take.
Ramban: See Bereishis 10:13, 14.
Ramban, Da'as Zekenim, Hadar Zekenim and Rosh : Based on the principle that 'Ayin' and 'Ches' are interchangeable (See Ramban, DH 've'Al Da'ati').
See Ramban DH 'u'bi'Bereishis Rabah', who, citing the Midrash, elaborates on the names 'Refa'im' and Avim. He also explains that the Chivi are not listed in Bereishis 15:19-21, because they are synonymous with the Refa'im who are mentioned there (See Ramban DH 'v'Al Da'ati').
Ramban: A descendant of Edom. Since Kaftorim took it their land, it became permitted to Yisrael.
Rashbam: By changing the "Ayin in "Avis" to an 'Alef''. See Rashbam.
See Torah Temimah, citing Chulin, 60b, and note 10 & 11.
See Oznayim la'Torah
What happened to the Avim afterwards?
Ramban: After the Kaftorim conquered land from the Avim as far as Aza, which is the south-western border of Eretz Yisrael, 1 they divided it among their five princes, 2 leaving the rest of their land intact. 3 And since the land was called Pelashes, they became known as the P'lishtim. The Kaftorim exiled the Avim to Kaftor, which is part of Egypt. And at some unknown stage, Hashem returned them to their land. 4
Ramban: See Bereishis 10:19.
Ramban: Aza, Ashkelon, Ashdod, Gas and Ekron.
Ramban: As is evident in Yehoshua, 13:3.
Which explains why the Pasuk in Yehoshua mentions them. See Ramban DH 've'Hinei' who discusses the relationship between Yisrael and the P'lishtim.
Why does the Torah write that the Avim lived in open towns?
Da'as Zekenim, Hadar Zekenim and Rosh: To convey their strength, on accont of which they felt no need to fortify their towns.
