On October 5, One Wakeel Ahmad was admitted to Sanjay Gandhi Memorial Hospital in a serious condition with a stab wound on the left side of his chest, they said.
The hospital authorities informed police about the patient.
Later, the victim succumbed to his injuries, the police said, adding a case was registered at Aman Vihar police station in this connection.
Ahmad's brother told police that Vishal and his brother- in-law were involved in the killing.
During interrogation, Vishal told police that he along with his brother-in-law Anil stabbed Ahmad to death, said Deputy Commissioner of Police (Outer) Pankaj Kumar Singh.
The arrested accused suspected that Ahmad was in a relationship with his wife. Police also recovered the knife used in the commission of crime.