When will they say so?
Rashi: When they see this.
Malbim: At the time of the redemption.
Why does he thank Hashem for being angry at him?
Rashi: You exiled me, and my Galus atoned for my sin, and turned back Your anger, and You consoled me. Radak - and You did not leave me in Galus, like I deserved.
Rashi citing Targum Yonasan: I will thank You, for I sinned against You, and if not for Your mercy, I would not merit to return Your anger and [for You] to console me. And behold, Your anger returned from me!
Sha'arei Teshuvah 4:12: I thank You for Your Musar (chastising). I accepted it with love. Due to this, that I thank You for being angry at me, Your anger departs, and You console me.
Orchos Tzadikim (Sha'ar ha'Simchah DH v'Chen keshe'Yesh): Many evils are good in the end. A parable is two men who were going to embark on a boat. One got a thorn in his foot, and was unable to go; his colleague went. He was cursing his [bad fortune that] day; later, he heard that the boat sank and all the passengers died. He praised Hashem, for he saw that [he got the thorn] in order to keep him alive.
Malbim: "Anaf" teaches that he sees an angry face. Chemah is bearing hidden hatred. He thanks Hashem for showing anger and punishing for his sin. Had he guarded the anger inside, there would be no solution.
Why does it say "u'Snachameni"?
Sha'arei Teshuvah: Refer to 12:1:2:3.
Malbim: This is like one who harmed his friend, and was appeased with him. He consoles him for the pain that he suffered.
