A gang of five men stormed a house in Rotherham and attacked an occupant before fleeing with cash and a mobile phone.
The men struck in Oxford Street, Clifton, in the early hours of Wednesday, February 10 but South Yorkshire Police has only today released details.
Detectives investigating the incident said the men all wore dark clothing and had scarves around their faces.
They attacked a 64-year-old man, leaving him with cuts to his face and mouth.
Detective Sergeant Graham Stead said: “This was a nasty and aggressive attack that has caused the family significant distress.
“We are working with them to offer support and reassurance.
“An investigation is underway and anyone with information is asked to contact police.”
Call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.