Who is "Eved Melech ha'Kushi"?
Rashi: The Eved is Baruch ben Neriyah. Kushi is Tzidkiyah (Mo'ed Katan 16b). Just like a Kushi's skin is different [than other people's - it is black], so Tzidkiyah was different than his entire generation (they were Resha'im).
Rashi citing Sifri (Bamidbar 99) Midrash: Kushi is Baruch 1 .
Radak #1: He was a servant of the king, a Kushi [and a Seris].
Radak citing Targum Yonasan: He was a servant of the king.
Radak #2: The name of this Kushi was 'Eved Melech.' If not, why does it say everywhere 'Eved Melech', and never ha'Melech? If Melech refers to Tzidkiyah, it should say ha'Melech! Also, why is this servant's name never mentioned? Rather, his name was Eved Melech, like we find Achimelech and Avimelech.
Just like a Kushi's skin is different, so Baruch was different than all people of the palace. (Also "Eved Melech" refers to him. - PF)
What is the meaning of "Ish Saris"?
Rashi citing Targum Yonasan: A great man.
Radak: He was a eunuch.
