What is "u'va'Midbar Asher Ra'isa ... " referring to?
Rashi: It is a continuation of the previous Pasuk - 'Hashem will fight for you like all that He did for you in Egypt ... and subsequently, in the desert ... '.
Oznayim la'Torah: "u'va'Midbar Asher ... Ra'isa Ka'asher Yisa Ish Es B'no" is in answer to Yisrael's claim "be'Sinas Hashem osanu" in Pasuk 27. 'How could you say such a thing when you saw how Hashem led you in the desert like a father leads a son - even when punishing you". 1
Targum Yonasan: "u'va'Midbar Asher Ra'isa ... " refers to the highly venomous snakes that they saw in the desert, and which the Cloud had killed. 2
What is Moshe referring to when he states "Ka'asher Yisa Ish Es Bno ..."?
Rashi: It refers to Hashem's protection of Yisrael. Refer to Sh'mos, 14:20:1:1*.
