2. cup of trembling—a cup causing those who drink it to reel (from a Hebrew root "to reel"). Jerusalem, who drank the "cup of trembling" herself, shall be so to her foes (Isa 51:17, 22; Jer 13:13). Calvin with the Septuagint translates, "threshold of destruction," on which they shall stumble and be crushed when they attempt to cross it. English Version is better.
both against Judah—The Hebrew order of words is literally, "And also against Judah shall he (the foe) be in the siege against Jerusalem"; implying virtually that Judah, as it shares the invasion along with Jerusalem, so it shall, like the metropolis, prove a cup of trembling to the invaders. Maurer with Jerome translates, "Also upon Judah shall be (the cup of trembling); that is, some Jews forced by the foe shall join in the assault on Jerusalem, and shall share the overthrow with the besiegers. But Zec 12:6, 7 show that Judah escapes and proves the scourge of the foe.