Gevurahגבורה

The power to say no. Gevurah — also Din (Judgment) and Pachad (Fear) — contracts, limits, burns away. Without it Chesed's flood would erase all difference; with too much of it, evil itself is born: the Zohar and Luria both locate the root of the Sitra Achra, the Other Side, in judgment separated from mercy. Fire, the left hand, the fear of Isaac. Every boundary you have ever loved was drawn here.

The Idra teaches that the lower world's harsh judgments are sweetened only "in their root" — by tracing Gevurah back up into the beard of mercy.