Harshwardhan Shah, the complainant, alleged that brothers Parag and Devang Dave, along with another unidentified man, accosted him near his house in Isanpur area late last night, and had a quarrel with him over the will of Daves' aunt.
Following this, they allegedly set him on fire after pouring petrol on him, Assistant Commissioner of Police RC Pathak said.
Shah, who suffered 40-45 percent burn injuries, was admitted to LG Hospital and his condition was stable.
According to police, sometime ago, Devang had taken Shah, his friend, to Mumbai where Shah stood witness to a will of Devang's aunt.
The will bequeathed property worth crores of rupees on Devang. But after her death, other relatives challenged the will and Daves wanted Shah to remain present during litigation before the Mumbai court.
His reluctance led to yesterday's incidence, police said.
Police have registered a case under the section of 307 of the Indian Penal Code (attempt to murder) and arrested Devang, while two others are yet to be traced.