Robbers attacked a man with an iron bar leaving him with a broken jaw, fractured ribs and head injuries after stealing £7 from him.
The 39-year-old man was assaulted as he walked home from a friend's house in Knotty Ash, Liverpool on Thursday.
Shortly after handing £7 to two men who threatened him, another two men got involved and started to attack him with the iron bar.
Detectives described it as a "ruthless" beating.
The offenders, who were all in their late teens or early 20s and were wearing black clothing, fled the scene leaving him on the street.
The victim managed to flag down a passing taxi and, with the help of two male passers-by, managed to get to a medical centre in Old Swan before being transferred to hospital.
Det Insp Eddie Cowan said: "This was an extremely serious and completely unprovoked assault in which the victim has received extensive injuries from a group who ruthlessly beat him, all for just £7.
"I would particularly like to hear from the two passers-by that helped our victim get medical attention, they could have some important information."