Rashi: It means that, due to this particular encampment, in which the miracle hinted at in the next Pasuk took place, the following will be said ...

Rashbam: Following the journeys in which Yisrael backtracked and went around Har Se'ir ¹ (the land of Edom), when they came across the well mentioned above - in 20:8 - they added to the praises to Hashem on the miracles of the Yam-Suf of the streams of Arnon also the praises of the miracle of the well, which initially they did not do, because Moshe and Aharon were punished through it.

Rashi and Seforno: The Pasuk means simply that, when people talk of the miracles that our ancestors experienced, they will also relate the current miracle. ¹

Ramban, Seforno and Da'as Zekenim: It is a book written by the historians ² of those times in which they would record the major battles that had been fought; ³ and the great victories they would ascribe to Hashem. Here it discusses Sichon's conquest of Mo'av. ⁴

Targum Onkelos: It is a book that records all the miracles that Hashem performed at the Yam-Suf and His mighty deeds at the rivers of Arnon.

Targum Yonasan: It actually refers to the Book of the Torah, which records the battles of Hashem.

Moshav Zekenim (citing R. Yehudah ha'Chasid): It refers to Seifer Devarim, which records the wars and victories of Yisrael - "u've'Se'ir Yashvu ha'Chorim Lefanim u'Venei Eisav Yirashum", "Kaftorim? Hishmidum" (Devarim 2:12 & 23). In all cases the strong conquered the weak, but Yisrael dispossessed the strong.

Kidushin, 30b: It hints at two Chachamim ? even a father and son, a Rav and his Talmid - debating in Torah and fighting with each other like enemies, ⁵ will ultimately become best friends (?es Vahev be'Sufah? ⁶ (from there they grow like rivers [?ha'Nechalim?] and become great and inherit ⁷ Torah - Moshav Zekenim).

Seforno: In deference to Moshe and Aharon ? because it includes praise of the well?s supernatural properties ? when it miraculously carried the blood and bones of the corpses from the valley to the heights, which the Torah had to do because Moshe and Aharon failed to do so - by causing it to produce water only after striking it instead of speaking to it. ¹

Rashi and Rashbam: It means 'What he gave them ¹ at the Yam-Suf' (with reference to the miracles that occurred there). ²

Ramban: With reference to Sichon's defeat of Mo'av, ³ which everyone considered a great miracle, the Pasuk is describing it as the storm ⁴ that hit Mo'av. ⁵

Seforno: Refer to 21:14:4:3.

Targum Onkelos: With reference to the beginning of the Pasuk, "be'Sufah ve'es ha'Nechalim Arnon" means that it is written in the Seifer Milchamos Hashem the battles that Hashem fought at the Yam-Suf and His acts of might by the streams of Arnon.

Targum Yonasan and B?rachos, 54a): It refers to Es ⁶ and Hav, two Metzora'im who walked at the edge (?be?Sufah?) of the camp, who witnessed the miracles that the Torah is referring to, and informed the people how, when the B?nei Amon and Mo?av hid in the caves in the mountains ⁷ to kill Yisrael as they passed in between them, ⁸ the two mountains came together ⁹ and squashed them. ¹⁰

Da'as Zekenim: ?Es-Vahev? is one word, like "be'Hisvada Yosef" (Bereishis 45:1). Here it is like ?Isyahev? (was given - Melech Mo'av was defeated) in the 'storm', and all his land was taken until the Nachal.

Rashi, Rashbam and Targum Onkelos: It means that, just as people will speak about the miracles of the Yam-Suf, so too will they speak about the miracles of the streams of Arnon. ¹

Ramban and Hadar Zekenim: This refers to the rivers up to Arnon, (all of which Sichon attacked and took ² from Mo'av by storm). ³

Seforno: The miracle of the storm-winds ⁴ that Hashem blew that caused the rivers to swell, thereby preventing Sichon (the Emori) from attacking Yisrael as they passed through his land in peace ⁵ is recorded in the Seifer together with the other battles that Hashem fought.

Targum Yonasan and B?rachos, 54b: It refers to the rivers of blood of the B'nei Edom and the B'nei Mo'av flowed down to the valley that was next to Arnon