1)
Who said "Ed"?
1.
Rashi (from Makos 23b): A Bas Kol said it. This is one of three places in which Ru'ach ha'Kodesh appeared in a Beis Din below. 1 Radak - Hashem said, you testify about what is revealed. I testify about what is hidden. Malbim - a Shofet oversees public taxes and Tzedakah. He is allowed to take his wage and income from there; only Hashem could testify that he did not. "Va'Yomer" refers to Hashem earlier in the verse.
2.
Radak: It was all of Yisrael together. Therefore, it is in the singular.
1
Makos 23b: The others are "Tzadkah Mimeni" (when Tamar was being judged) and "Hi Imo" (when Shlomo decided who is the mother of the live baby.
