What is the meaning of "Haysah Yehudah Lekadsho"?
Rashi: Hashem took Yehudah for His portion and Kedushah, and Yehudah sanctified His name at the sea. Refer to 114:2:2:1.
Radak: Hashem took [Yisrael] from a Tamei nation, and made them a Goy Kadosh.
Malbim: Hashem's conduct with His Kedushah caused Yehudah to be Moser Nefesh for Kedushas Hashem.
Why does it say "Yisrael Mamshelosav"?
Rashi: Because [Nachshon of] Yehudah entered Yam Suf first 1 , Yehudah merited to rule over Yisrael). Refer to 114:3:1:1.
Radak: Hashem took them from Egypt's rule, so they would be only under His rule - "v'Atem Tihyu Li Mamleches Kohanim v'Goy Kadosh" (Shemos 19:6). You will be a kingdom unto itself, and Kohanim and servants to Me.
Malbim: Hashem showed His authority to rule over nature and do wonders, this was via Yisrael's deeds. Refer to 114:3:1:1.
Mechilta d'R. Yishmael (Beshalach, Masechta d'va'Yhi Pharaoh 5) adds 'and his Shevet after him.' Radak - and after them, all of Yisrael.
Why does it say first Yehudah, and afterwards Yisrael?
Radak: From when they left Egypt, Yehudah was at the head, and traveled first, like Yakov's Brachah "Yehudah Atah Yoducha Achecha" (Bereishis 49:8).
