Why is "Ki Va" repeated?
Radak: The repetition is to strengthen the matter.
Malbim: This coming will be via natural orders. It is as if first He came and influenced the natural order in Shamayim, and came a second time to judge the land. The latter is via people's actions; two conducts are used together. Refer to 96:13:2:2.
Is there a difference between "Lishpot ha'Aretz" and "Yishpot Tevel [b'Tzedek v'Amim be'Emunaso]"?
Radak: The end of the verse explains what came before.
Malbim: The latter explains two ways of judging. Judgment via Emunah is based on fixed natural laws; it is being faithful to what shat came before. Tzedek looks into people's deeds, and conducts according to reward and punishment. This conduct of Hashgachah via nature fulfils both Tzedek and Emunah.
