Why does it say "ha'Tzari Ein b'Gil'ad"?
Rashi: Sap comes from there - "Ali Gil'ad u'Kchi Tzari" (46:11). This is a parable - were there no Tzadikim to learn from, and improve your ways?! Radak - the parable is, is there no doctor to cure My nation? (Sap is used to cure harsh illnesses , e.g. a snake bite.) I.e. is there no Chasid among them, that Hashem will atone for them due to him?
Radak citing Targum Yonasan: Yirmeyah said, do I not have good deeds to request [salvation] for Yisrael? I always yearned to learn from Eliyahu ha'Navi from Gil'ad!
Malbim: Hashem answers, did Yehudah need a cure from afar? Sap (a potent medicine) is common in Yehudah, and also doctors! The cure was to improve their deeds - I gave to them Torah and Mitzvos, and Nevi'im and Chachamim (doctors to instruct how to take the medicine). We must say that they did not want to be cured.
Ta'anis 4a according to Rashi there, Otzar Midrashim Chupas Eliyahu p.168: Why did Yiftach offer his daughter for an Olah? Was there no remedy and doctor? Pinchas could have permitted Yiftach's vow! Refer to Shoftim 11:35:3:1 and the notes there.
What is the meaning of "Lo Alsah Aruchas"?
Rashi: It was not cured.
