3. sat--expressing military occupation or encampment.
      middle gate--the gate from the upper city (comprehending Mount Zion) to the lower city (north of the former and much lower); it was into the latter (the north side) that the Chaldeans forced an entry and took up their position opposite the gate of the "middle" wall, between the lower and upper city. Zedekiah fled in the opposite, that is, the south direction (Jer 39:4).
      Nergalsharezer, Samgarnebo--proper names formed from those of the idols, Nergal and Nebo (2Ki 17:30; Isa 46:1).
      Rab-saris--meaning "chief of the eunuchs."
      Rab-mag--chief of the magi; brought with the expedition in order that its issue might be foreknown through his astrological skill. Mag is a Persian word, meaning "great," "powerful." The magi were a sacerdotal caste among the Medes, and supported the Zoroastrian religion.

JFB.