Isaac Luria taught that, when the world was made, God’s infinity was too great to be contained, and creation shattered. The world that we know consists of broken vessels, with sparks of God trapped inside. We bless this cup to remind us of our obligation to find the holy sparks in our broken world, and to fix what must be mended. 

haggadah Section: Nirtzah
Source: Velveteen Rabbi's Haggadah