Rashi: Enemies who will dispossess you, who dwell in Morashah. It says ha'Yoresh, for this is like Morashah. Radak - Morashah is in Yehudah. The enemy will exile you and inherit it. "Avi" is written without the Aleph at the end, like "Al Yani Roshi" (Tehilim 141:9).

Rashi citing R. Menachem: Bnei Eilam were proper to inherit Eretz Yisrael ? he was Shem's firstborn (Bereishis 10:22). Due to My love of your fathers, I transferred it to [Yisrael, who are from] Bnei Arpachshad. Now I will bring Kasdim and Bnei Eilam against [Yisrael].

Malbim: You did not gain from this at all, for Malchei Yisrael were like Achzav, and did not guard their promise. They themselves took Morashah from you. Initially only Pelishtim wanted to take Morashah ? now I bring another against you who wants to dispossess it!

Rashi: Adulam is inside the border. The honor of Yisrael will recede, for the Nochrim will capture from the border until Adulam. So Yonason translates.

Radak: Adulam is in Yehudah. "Ha'Yoresh" applies also to Kevod Yisrael (he will dispossess it). It refers to Melech Ashur ? "Alah Sancheriv Melech Ashur Al Kol Arei Yehudah ha'Betzuros va'Yispasem" (Melachim II, 18:13).

Malbim: It did not suffice for them to take Morashah ? the new Yoresh will come until Adulam, which was also a fortified city in that area. It is counted among the fortified cities that Rechav'am built (Divrei ha'Yamim II, 11:7). Pekach took also Adulam. Who is this Yoresh? Kevod Yisrael ? the camp of Melech Yisrael and his honor.