וַיִּכְתֹּ֥ב מֹשֶׁ֛ה אֶת־הַשִּׁירָ֥ה הַזֹּ֖את בַּיּ֣וֹם הַה֑וּא וַֽיְלַמְּדָ֖הּ אֶת־בְּנֵ֥י יִשְׂרָאֵֽל׃
Maka pada hari itu Musa menuliskan nyanyian ini, lalu mengajarkannya kepada orang Israel.
Ibn Ezra
Scripture says eleven days to tell us that Moshe spoke these words during those eleven days wherein they traveled from Ḥorev to Qadesh Barnea. I shall later inform you that the spies started out from Qadesh Barnea [comment on: 3] [see also Numbers 32: 8]; after God swore that they would not enter the land, no new commandments were given until the fortieth year — for so it is written [Bava Batra 121a–121b] [Ta‘anit 30b] [cf. 2: 16–17]. Conclusive evidence is found in the phrase “to expound this Torah” [: 5]: He explained the Torah that he had already spoken between Paran and Tofel. Note that most of the Commandments are repeated in this book. Accordingly, the upcoming phrase “all that God had commanded him concerning them” [: 3] is properly modified by the preceding phrases “across the Jordan” [: 1] and “in the desert wilderness” [: 1]. If you can grasp the mystery behind the following problematic passages: 1) The final twelve verses of this book 2) “Moshe wrote…” [31: 22] 3) “At that time, the Canaanites dwelt in the land” [Genesis 12: 6] 4) “…In the mountain of God , He will appear” [Genesis 22: 14] 5) “behold, his bed is a bed of iron…” [3: 11] you will then understand the truth. There are those who say that the reason for mentioning It is eleven day’s journey from Ḥorev, by way of Mount S̀eir, to Qadesh Barnea is to stress that they wandered in the wilderness for forty years — hence, the contrasting phrase
Ramban
AND NOW WRITE YE THIS SONG. In line with the plain meaning of Scripture, He commands both Moses and Joshua to write it for He wanted to make Joshua His prophet during Moses’ lifetime. Now, Moses wrote it while Joshua stood by him, read it, and saw [it completed], this being the sense of the verse, So Moses wrote this Song the same day, and taught it the children of Israel.36Further, Verse 22. It refers to Moses who was the principal [in the writing of the Song] for it was from him that they would hear it and learn it, although Joshua, too, taught it with him, as it is stated at the conclusion [of the chapter] he [i.e., Moses], and Hoshea, the son of Nun.37Further, 32:44.
Now, the meaning of the expression this Song is “the Song that I will now tell you,” this being ‘Ha’azinu’ (Give ear).38Ibid., Verses 1-43. It is called Song because Israel would recite it with song and psalm.39At the Divine Service in the Sanctuary, a section of the Song of Ha’azinu was chanted each Sabbath during the Service of the Additional Offering. The cycle of the Song was completed every six weeks. Therefore, the six divisions (Aliyoth) in the reading of this Song in the Synagogue on the Sabbath of Ha’azinu, follow the same divisions as sung in the Sanctuary (Rosh Hashanah 31a). It was also written [in the Torah] in the style of a song, since songs are written with interruptions [empty spaces] indicating the places of chanting.
Now, the meaning of the expression this Song is “the Song that I will now tell you,” this being ‘Ha’azinu’ (Give ear).38Ibid., Verses 1-43. It is called Song because Israel would recite it with song and psalm.39At the Divine Service in the Sanctuary, a section of the Song of Ha’azinu was chanted each Sabbath during the Service of the Additional Offering. The cycle of the Song was completed every six weeks. Therefore, the six divisions (Aliyoth) in the reading of this Song in the Synagogue on the Sabbath of Ha’azinu, follow the same divisions as sung in the Sanctuary (Rosh Hashanah 31a). It was also written [in the Torah] in the style of a song, since songs are written with interruptions [empty spaces] indicating the places of chanting.
Or HaChaim
You will find that Moses complied with these instructions as we find in verse 22 that he wrote down the song and taught it to the Israelites. Only in the verse following did G'd give His instructions to Joshua to bring the Israelites across the Jordan, to be strong, etc. Normally, we would have expected G'd to complete all His various instructions and only then to write down this song (Haazinu) and to teach it to the people. Seeing that G'd did not want the normal procedure to be followed, He wrote the word ועתה, "and now."