What is the difference between Yach'iv and Yimchatz?
Devar Eliyahu: Some illnesses strike internal limbs, via Shamayim. Others are in external limbs via people, e.g. via a sword. These need human cures - "v'Rapo Yerapei." The former, and especially agony and pain from Shamayim, "Ani Hashem Rofe'echa." Yach'iv is the former - "v'Yechbash" (Hashem will heal it). Yimchatz is an external wound via a sword - even so, "Yadav Tirpenah."
Malbim: Yach'iv is Tochachah to fix his way. This is like wrapping a cloth over a wound, lest it spread - v'Yechbash. He will block the feelings of the Nefesh, lest he sin again. Yimchatz corresponds to great afflictions to atone for sins. His own hands will heal it, like one who gives bitter potions to a Choleh to cure him. The bitterness itself is the cure!
What is the meaning of "Tirpenah"?
Ibn Ezra: They will heal it. It is as if there is an Aleph in place of the Yud, like "Ripinu Es Bavel v'Lo Nirpasah."
