What is "Nachras Susav"?
Rashi: It is the sneezing of his horses. Radak - it is called so, for it comes from the Nechirim (nostrils).
Why does it say "mi'Dan"?
Rashi, Targum Yonasan: It is because they served [Yaravam's] calf in Dan.
Radak: It was the end of Eretz Yisrael.
Malbim: Bnei Dan 1 were skilled at fighting against cavalry - "Yehi Dan Nachash... ha'Noshech Ikvei Sus va'Yipol Rochvo Achor" (Bereishis 49:17). Dan traveled at the end of Machaneh Yisrael, because cavalry attack the back of the camp when they chase after them. If so, why are the enemy's horses heard from Dan?
What is "Mitzhalos Abirav"?
Rashi: It is the joyful neighing of horses 1 . We find that horses are called Abirim - "mi'Daharos Daharos Abirav" (Shoftim 5:22). This is like "v'Sus Doher" (Nachum 3:2).
Rashi citing Targum Yonasan: The steps of his Giborim.
Radak: This is like it says about horses "v'Yasis b'Cho'ach" (Iyov 39:21).
