Pirkei Avox for Shabbat Shirah aka Everyone Look At This Lovely Piyyut

(2) (Exodus 15:1) "Az yashir Moshe": Az ("then") sometimes means the past and sometimes means the future.

The past: (Genesis 4:26) "Az men began", (Exodus 4:26) "Az she said", (Exodus 15:1) "Az Moses sang", (Numbers 21:17) "Az Israel sang", (Joshua 10:12) "Az Joshua spoke", (I Chronicles 15:2) "Az David said", (I Kings 8:12) "Az Solomon said."

And sometimes "Az" means the future, viz.: Isaiah 60:5) "Az you will see and flow", (Ibid. 58:8) "Az your light shall break forth as the morning", "Then there shall be opened", (Ibid. 35:6) "Az the lame man shall leap as a hart", (Ibid. 5) (Jeremiah 31:12) "Az the virgin will rejoice in the dance", (Psalms 126:2) "Az our mouth will be filled with laughter", (Ibid.) "Az they will say among the nations."

Variantly: It is not written "Then Moses sang," but then Moses will sing" — whence we derive the resurrection from Scripture. (Exodus 15:1)

"this song": There are ten "songs."

The first, that sung in Egypt, viz. (Isaiah 30:29) "The song (of Sancherev's destruction [on Pesach night]) will be to you as that of the night on which you sanctified the festival (Pesach [in Egypt]), etc."

The second, that of the sea — "Then Moses sang."

The third, that of the well (Numbers 21:17) "Then Israel sang."

The fourth, that of Moses, viz. (Devarim 31:22) "And Moses wrote this song (32:1-43).

The fifth, that of Joshua, viz. (Joshua 10:12) "Then Joshua spoke to the L rd on the day the L rd delivered, etc."

The sixth, that of Devorah and Barak, viz. (Judges 5:1) "And Devorah and Barak the son of Avinoam sang, etc."

The seventh, that of David, viz. (II Samuel 22:1) "And David spoke to the L rd the words of this song, etc."

The eighth, that of Solomon, viz. (Psalms 30:1) "A psalm, a song of the inauguration of the Temple of David."

[[... there's a very beautiful digression here which I have cut out but which you should GO AND FIND]]

The ninth (song): (II Chronicles 20:21) "And he (Yehoshafat) took counsel with the people, and he set up singes to the L rd and lauders of majestic holiness. When they went out before the vanguard they said; 'Give thanks to the L rd, for His lovingkindness is forever!'" Why is this thanksgiving different from all the others in the Torah, where it is written "Give thanks to the L rd for (the good, for His lovingkindness is forever"? __ It is to say, as it were, that there is no rejoicing before Him over the destruction of the wicked. If over that of the wicked there is no rejoicing, how much more so (is there grief) over that of the righteous, one of whom is over and against the entire world, viz. (Mishlei 10:25) "And the righteous one is the foundation of the world."

The tenth (song) in time to come, viz. (Isaiah 42;10) "Sing to the L rd a new song, His praise from the end of the earth (Ibid. 48:42) "Say: The L rd has redeemed His servant Jacob. All of the (other) songs are denominated in the feminine ("zot"). Just as a female bears (and then travails again), so, the past salvations were followed by subjugation. But the future redemption will not be followed by subjugation — wherefore it is denominated in the masculine ("zeh" [viz. Isaiah 26:1]). As it is written (Jeremiah 30:6) "Ask now and see if a male has ever given birth. Why, then, do I see that every man puts his hands upon his loins (as a woman giving birth?") For just as a male does not bear (and thus travail), so, the future redemption will not be followed by subjugation. As it is written (Isaiah 45:17) "Israel will be saved by the L rd, an eternal salvation. You will not be ashamed or abashed forever."

(1) R. Nechemiah says: If one takes upon himself a single mitzvah in faith, he is worthy of having the holy spirit rest upon him. And thus do we find with our ancestors that with the reward of the faith with which our ancestors believe in God, they merited and the holy spirit rested upon them and they spoke song, as it is written (Exodus 4:31) "And the people believed in God and in Moses His servant" and it is written "Then Moses and the children of Israel sang".

And so you find that Avraham our father only merited this world and the world to come in the merit of the faith with which he believed in God, as it is written "and he put his trust in the God, and He reckoned it to his merit."

And so you find that Israel was only redeemed from Egypt as a reward for faith, as it is written (Exodus 4:31) "And the people believed" And thus is it written (Psalms 31:24) "The L rd guards the faithful."

The faithfulness of the fathers is brought to remembrance, viz. (Exodus 17:12) "And Aaron and Chur supported his (Moses') hands, and his hands were (lifted in) faithfulness until the sun set." And it is written (Psalms 108:20) "This is the gate to the L rd. Tzaddikim (faithful in prayer) will enter through it." What is written of the "believers"? (Isaiah 26:2) "Open the gates and let there enter a nation that is (a) tzaddik, a keeper of faith" — this gate is to be entered by all believers. (Psalms 92:2-5) "It is good to praise the L rd and so sing to Your exalted name. To proclaim in the morning Your lovingkindness, and Your faithfulness in the nights. With a ten-stringed harp, with voice and lyre together. For You have gladdened me by Your deeds, O L rd. At the work of Your hands I will sing." What made him worthy of this joy? The belief held by our fathers in this world, which is all "night." Thus, "to proclaim in the world (to come) Your lovingkindness and Your faithfulness in the 'nights'" (i.e., this world). And thus with Yehoshafat (II Chronicles 20:20) "And they rose early in the morning and they went to the desert of Tekoa. And as they went forth Yehoshafat arose and said: 'Hear me, Judah and dwellers of Jerusalem: Believe in the L rd your G d and you will rest assured. Believe in His prophets and you will succeed.'" And it is written (Jeremiah 5:3) "O L rd, are Your eyes not (looking) for belief?" (Habakkuk 2:4) "And the tzaddik in his belief shall live", and (Eichah 3:23) "They (Your mercies) are renewed every morning — Great is Your faithfulness." And thus do you find that the exiles are gathered in, only in reward for faith, as it is written (Song of Songs 4:8) "With Me, from Levanon, My bride; With Me from Levanon shall you come (out of exile). You shall look (upon the redemption) merosh amanah" (homiletically: "in the merit of emunah [belief]). (Hoshea 2:22) "And I will betroth you to Me forever … and I will betroth you to Me with emunah."