Musar sur Nahoum 1:6

The reason that repentance is such a powerful tool is that it ranks higher than all the accusers [in the Celestial Spheres], and those who address themselves to that "power" need not be afraid of any evil forces in the world. We know this from such verses as Isaiah 14,27: כי ה' צבאות יעץ ומי יפר, וידו הנטויה ומי ישיבנה. "For the Lord of Hosts has planned it, who could possibly foil it? We also read in Nachum 1,6:לפני זעמו מי יעמוד! "Who can stand up to His wrath!" The word Mee in both these verses refers to the institution of repentance. We know this from Isaiah 40,26: "שאו מרום עיניכם וראו מי ברא אלה" as well as from Isaiah 40,14: "את מי נועץ ויבינהו?" "Raise your eyes heavenwards and behold, who has created all these?" Or, "With whom did He consult, and who taught Him?". We have the verse מי א-ל בשמים ובארץ, which means that the Lord of Heaven and earth is called מי, "Who", seeing no one can comprehend His Essence. This is the mystical dimension of the word מי. When the prophet Isaiah 41,4 says: מי פעל ועשה, "Who has labored and brought to fruition," he reveals a deep secret. Heavenly decrees are reconsidered in the upper emanation of בינה or in the lower emanations of נצח and הוד respectively. The latter regions are known as G–d's צבאות. A righteous person who wants to annul someone else's vow concentrates on the region in which G–d annuls such decrees. Eicha Rabbah 3, explains the verse in Lamentations 3,44, סכותה בענן לך מעבור תפלה, "You have screened Yourself off with a cloud, so that no prayer may pass through." Our sages refer to the story involving Rabbi Chanina bar Papa. This rabbi approached Rabbi Samuel who had a reputation of being an expert in homiletics, asking him to explain this verse to him. The latter explained that the verse means that there are times when the gates of prayer are locked, and other times when they are open. He quoted Rabbi Yossi ben Chalafta who had said that there are times when it is propitious to offer prayer, based on the verse in Psalms 69,14: "As for me, may my prayer come to You My Lord, at a favorable moment." The gates of repentance however, are never locked, since repentance is compared to the ocean which is never sealed, and accepts waters from the rivers at all times.