מדרש אויף ירמיהו 31:12

(Exodus 15:1) "Az yashir Mosheh": Az ("then") sometimes signals the past and sometimes signals 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" signals 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."

Then sang Moses. At times the word then refers to events that happened in the past, and at other times it refers to events that are to transpire in the future. The word then refers to past events in the following verses: Then began man to call upon the name of the Lord (Gen. 4:26), Then she said: “A bridegroom of blood” (Exod. 4:26), Then sang Israel this song (Num. 21:17), Then Solomon spoke (I Kings 18:12). All of these refer to past events. Instances in which the word then alludes to future events are: Then thou shalt see (Isa. 60:5), Then shall thy light break forth (ibid. 58:8), Then shall the lame man leap as a hart (ibid. 35:6), Then the eyes of the blind shall be opened (ibid., v. 5), Then shall the virgin rejoice (Jer. 31:13), Then was our mouth filled with laughter, and our tongue with singing (Ps. 126:2), and Then said they among the nations (ibid.). All these allude to future events. From this we learn that the concept of the resurrection of the dead is derived from the Torah.

“To whom the word of the Lord came… until the end of eleven years of Zedekiah son of Josiah, king of Judah, until the exile of Jerusalem in the fifth month.” (Jeremiah 1:2-3) R’ Avon said: the lion (ari) came up during the constellation of the lion and destroyed Ariel. ‘The lion came up’ refers to Nebuchadnezzar the wicked, as it is written “A lion has come up from his thicket…” (Jeremiah 4:7) ‘In the constellation of the lion’, “…until the exile of Jerusalem in the fifth month.” (Jeremiah 1:3) ‘And destroyed Ariel’, “Woe, Ariel, Ariel, the city wherein David encamped!” (Isaiah 29:1) This happened in order that the lion would come in the constellation of the lion and rebuild Ariel. ‘The lion would come’ refers to the Holy One, as it is written “A lion has roared; who will not fear?” (Amos 3:8) ‘In the constellation of the lion’, “…and I will turn their mourning into joy…” (Jeremiah 31:12) ‘And rebuild Ariel’, “The Lord is the builder of Jerusalem; He will gather the outcasts of Israel.” (Psalms 147:2)