The three fled the spot after the incident yesterday and are on the run, Gumanpura police station Sub-Inspector (SI) Hansraj said.
An argument had broken out last evening between the victim, Devilal Prajapat, and his 50-year-old son over erecting a pillar to lay a water pipeline over the roof of his house.
The son and his wife then dragged the elderly man out of his residence in Kotari-Goverdhanpur area here and thrashed him, the SI said.
He was rushed to Maharao Bheem Singh (MBS) hospital where the doctors declared him brought dead.
After a complaint by the younger son of the deceased, police have lodged a case under relevant sections of the IPC against the three.
The man's body was handed over to his family members today after a postmortem examination and a hunt is on for the accused, police said.