What is the Story of Shambuka Vadha by Rama (Rama killing Shambuka)? Padma Purana mentions the story of Shambuka Vadha as a conversation between Bhisma and Pulastya.
Shambuka Vadha story goes like this..
After killing the demons king Ravana, Sri Rama returned to Ayodhya. Many sages had arrived there to bless him on the occasion of his crowning ceremony. Sage Vashishtha was one of them.As Sri Rama was conversing with the sages a brahmin arrived there with the corpse of his son and wailed—“O son! Your death is certainly due to some flaw of Sri Rama. Now, your mother and I have decided to give up our lives as there is no point in living.”
Sri Rama’s heart was filled with grief and he asked Sage Vashishtha as to how the brahmin could be helped. Sage Vashishtha revealed to Sri Rama that the brahmin’s son had died a premature death because of Shambuk. Vashishtha said–“Shambuk is a Shudra by birth, but he is doing an austere penance. Shudras are not entitled to do penance in all the three yugas, except the Kali Yuga. So, only his death can bring back the brahmin’s son alive.”
Sri Rama instructed both his younger brothers – Lakshman and Bharata, to look after the state’s affairs in his absence and went in search of Shambuk boarded on his Pushpak Vimana. Sri Rama saw a man doing penance at the shore of a reservoir. He landed his Pushpak Vimana and went near that man. He introduced himself and enquired about the man’s identity. Sri Rama asked–Why are you doing such an austere penance. Who are you?
Without moving the man replied that he was a shudra named Shambuk. He said— I am desirous of attaining to devaloka and hence I am doing this penance. Sri Rama took out his sword and severed Shambuk’s head. All the deities hailed Sri Rama and the brahmin’s child became alive once again.