(Devarim, Ibid.) "together, the tribes of Israel" — when they constitute one unit, and not when they are divided into many factions, as it is written (Amos 9:6) "Who builds His heights in the heavens and His bond on earth endures." — R. Shimon b. Yochai says: This is analogous to one's bringing two ships, connecting them with braces and bars, and building stately edifices upon them. So long as the ships are bound, the edifices endure; once the ships separate, the edifices no longer endure.
So, with Israel: When they do the will of the L-rd, their heights are in the heavens and His bond on earth endures. Similarly, (Shemoth 15:20) "This is my G-d and I will extol Him ("ve'anvehu"): When I acknowledge Him, He is "beautiful" ("naveh, as in ve'anvehu"), and (even) when I do not acknowledge Him," He is "beautiful." Similarly, (Isaiah 43:12) "And you are My witnesses, says the L-rd, and I am G-d ("Kel")": When you are My witnesses, I am G-d, and if you are not My witnesses I am not G-d" (i.e., I do not manifest Myself as "Kel").
Similarly, (Psalms 23:1) "To You I have raised my eyes, Who dwells in Heaven." If not, I would not dwell in heaven. Here, too, "together, the tribes of Israel" — when they are one bond (agudah), and not when they are of many agudoth (factions). Thus, "together the tribes of Israel."