WHAT IS THE MEANING OF BREAKING THE GLASS UNDER THE CHUPAH?
The glass is broken as a commemoration for the destruction of the Temple. The initial custom was to place ashes on the head of the groom, and from here the custom of breaking a glass evolved (Perishah, Even Ha’ezer 65:6).
Some have written that breaking the glass is also a metaphor for the finality of the bond that has been established. Just as a broken glass can never be reconstructed, so, too, we pray that this relationship last forever.
Sources: See also Berachos 30b-31a. Together with breaking the glass, some recite the verse in Psalms: “If I forget you, O Jerusalem, let my right hand forget [its dexterity]. Let my tongue cleave to my palate if I will not remember you; if I will not bring Jerusalem to mind during my greatest joy.”