In Indian society, rice is considered as symbol of wealth and prosperity.According to the Hindu tradition, as the bride steps out of the house, she throws back five handful of rice over her head, in a way that it falls on the person standing behind her.
The custom of throwing rice signifies that the bride is paying back or returning, whatever her parents have given her in all these years of her stay with them and wishes for prosperity to always flourish in the house she is leaving behind.