How will Egypt know Hashem?
Rashi: They will know His strength.
Radak: Initially, they knew Him from when He struck Machaneh Ashur. Now they will know and recognize that He saves them whenever they call to Him.
It already said "v'Noda Hashem l'Egypt." Why does it add "v'Yad'u Egypt Es Hashem"?
Malbim: Via Hashem helping Egypt, they will begin to contemplate Him and understand His general and individual deeds, via their intellect.
Why does it say "v'Avdu Zevach u'Minchah"?
Radak #1: This is like v'Asu Zevach u'Minchah. The Targum of Ma'aseh is Uvda. Also "va'Avodas ha'Tzedakah" (32:17, is doing Tzedakah).
Radak #2, Targum Yonasan: They will serve Hashem via Zevach and Minchah [Malbim - on the Mizbe'ach in Egypt].
What vow will they take to Hashem?
Radak: At the time of their affliction, they will vow and fulfill after they are saved, for they will recognize that Hashem saves them.
