Why does it say "Gam Yehudah"?
Rashi: Also Yehudah was foolish and ruined [their deeds].
Radak #1: Also Yehudah set itself to serve idolatry, like Efrayim, even though the Mikdash was in Yehudah's portion.
Radak #2: "Yehudah" calls out to Yehudah, like "Yehudah Atah Yoducha Achecha" (Bereishis 49:8). I.e. also you, Yehudah, planted a foreign sapling. Yisrael and Yehudah were friends, like it said "b'Shuvi Shevus Ami" via Yaravam ben Yo'ash Melech Yisrael, for I saw "Oni Yisrael Moreh Me'od" (Melachim II, 14:26). Yaravam returned Damesek and Chamas to Yehudah (ibid. 28), and even so, Yisrael and Yehudah did not repent.
Radak citing Targum Yonasan: Also Beis Yehudah [began to increase guilt. Also to them will come liability when I return the captivity of My nation.]
Malbim: Above, it said "Mah E'eseh Lecha Efrayim Mah E'eseh Lecha Yehudah v'Chasdechem ka'Anan Boker" (4). First the Navi discussed Efrayim's sin ? killing the Nevi'im. Now it teaches that also Yehudah's Chesed is like a morning cloud.
What is the meaning of "Shas Katzir"?
Rashi: He set the time of her punishment when she will be removed and exiled. This is like "Od Me'at u'Va'ah Es ha'Katzir Lah", regarding Bavel's punishment in Yirmeyah (51:33).
Radak: This is like "v'Asah Katzir Kemo Nata" (Iyov 14:9). Also [Yehudah] planted a foreign sapling, like Efrayim.
Malbim: Yehudah will reap the fruits of the Chesed it planted when I return My nation's captivity ? "Zir'u Lachem li'Tzdakah Kitzru l'Fi Chesed" (10:12). This was in the days of Chizkiyah; Hashem returned their captivity and saved them ? "v'Yasfah Peleitas Beis Yehudah ha'Nish'arahShoresh l'Matah v'Asah Pri l'Ma'alah" (Yeshayah 37:31).
What is "b'Shuvi Shevus Ami"?
Rashi: He rebuked them to repent from their wildness. This is like "Vanim Shovevim", "ha'Bas ha'Shovevah" (Yirmeyah 3:14, 31:21).
Radak: When I thought to return the captivity of My nation, for not all of them served idolatry. However, after also Yehudah served idolatry, I left them in the hands of their enemies.
