Why does the Torah write "al-Pi Hashm Yis'u ? ve'al-Pi Hashem Yachanu" ? ve'al-Pi Hashem Yachanu" - and not simply "al-Pi Hashm Yis'u Veyachanu"?
R. Bachye: Because they refer to Midas ha'Din and Midas Rachamim respectively - bearing in mind that when they traveled they were going to war (against the Cana'anim) 1 and when they encamped they rested from their travels. 2 3 4
Refer also to 10:35:5:3*.
R. Bachye: Because 'Whenever Yisrael gather together in their thousands and tens of thousands the Midas Rachamim is with them'.
See R. Bachye who explains how the two Midos work hand in hand and elaborates.
R. Bachye (on 10:2): This also explains why they blew a Teki'ah when they encamped and a Teru'ah when they traveled.
What procedure did Yisrael follow when they had to travel?
Rashi (citing the Sifri) and Targum Yonasan (in 9:35): When Yisrael needed to travel, the Pillar of Cloud folded and hovered above the camp of Yehudah in the form of a beam, the Kohanim 1 blew Teki'ah, Teru'ah, Teki'ah. The camp of Yehudah did not move however, until Moshe prayed "Kumah Hashem ... ". 2
What procedure did Yisrael follow when they encamped?
Rashi (citing the Sifri) and Targum Yonasan (in 10:36): When the time came to encamp, the Pillar of Cloud piled up and hovered above the camp of Yehudah like a Sukah. However, it did not spread out over the entire camp of Yisrael until Moshe announced "Shuvah Hashem ... ". 1
See later 10:36. All this complies with Pasuk 23, "Al Pi Hashem be'Yad Moshe".
