출애굽기 14:31의 Musar

And concerning Moses, it is written : "In all my house he is faithful" (Num. 12:7). And it is said in the Midrash : "Great is faith before the Holy One, Blessed is He, for because of the merit of the faith that our fathers believed there dwelt upon them the Holy Spirit and they uttered song as it is said : 'And they believed in the Lord and in Moses His servent. Then Moses and the Children of Israel sang' " (Exod. 14:31, 15:1, Exodus Rabbah 22-23).

Jacob's descendants merited the same advantages in due course. They experienced that the sea was split for their sake, and they witnessed the "great hand" of G–d at work (Exodus 14, 31). Israel merited the “רקיע” when G–d descended to Mount Sinai traversing all seven Heavenly Regions each known as a different רקיע at the time He gave them the Torah, commencing His revelation with the words: "I am the Lord your G–d who has taken you out of Egypt" (Midrash Hagadol Exodus 19, 20 – slightly different wording). Israel's relationship with G–d's throne is alluded to in Jeremiah 17, 12: כסא כבוד מרום מראשון מקם מקדשנו, "O Throne of Glory exalted from of old, our sacred Shrine". The "throne" mentioned is the throne of G–d in His Heaven. The same prophet wrote in Lamentations 2, 1: (after the destruction of the Temple) ‘השליך משמים ארץ תפארת ישראל, "He cast down from Heaven to Earth the majesty of Israel." Our sages in Eicha Rabbah 2,2 commented on this verse: G–d said: "The only reason you have the audacity to annoy Me is the fact that Jacob's features are engraved on My throne; Here I fling it down in your faces!" At that point in time, the letter כ in the ירך of Jacob became dislocated. The three letters in the word ירך, thigh, are the respective first letters of the words ים, רקיע, כסא. The dislocation of Jacob's thigh joint is an allusion to the dislocation of G–d's throne. The numerical value of the word כף in the expression כף ירך יעקב, is 100. It is an allusion to the letter ק which is written smaller in Rebeccah's exclamation קצתי בחיי, in Genesis 27, 46. We had explained previously that that was an allusion to the destruction of the Temple as foreseen by Rebeccah. Allegorically speaking, if one removes the letter ק from Jacob's name, one is left only with יעב, meaning a cloud which blocks out the sun and the daylight. This is the deeper meaning of Jeremiah in Lamentations 2, 1: איכה יעיב באפו א-דני את בת ציון, "How has the Lord shamed (brought dark clouds) the daughter of Zion in His wrath." The prophet refers to the former distinction of Israel having been flung to earth.

The Midrash's question "By what merit did Israel sing the שירה,” is itself difficult to comprehend! It is the practice of the צדיקים to give thanks to G–d immediately upon receipt of the promise of a forthcoming event. The צדיק does not wait until the promise has been fulfilled. The expression of his gratitude is no more than a true reflection of his abiding faith in G–d. If Moses, nonetheless had delayed his song of thanksgiving until after the miracle promised had actually materialised, this was but due to his lack of confidence in Israel's faith. This is why the Torah waited to report that Israel believed both in G–d and in Moses His servant until after the successful crossing of the sea and the drowning of the Egyptians in it (14,31). Only then was Moses able to break out in song. I have found this answer to the query raised in the introduction of a book called ברכת אברהם.