Magic of light: Rules for lighting diya in home temple
It's safe to claim that lighting a diya has been a custom for millennia. Lighting a lamp has long been associated with dispelling darkness, both literally and metaphorically. In Hinduism, the lighting of a diya is rooted in Vedic traditions, where light is regarded as a symbol of enlightenment that dispels the darkness of ignorance. The flame is also typically associated with Agni, the fire god, and represents his divine presence and purifying power.
Source: indiatimes.com