The US female group LaBelle (lead singer Patti LaBelle) recorded it in 1975. It only got to number 17 in the UK but was a US number 1. All Saints had a number one with it in 1998 and then Pink et al last year.
It was first recorded by a group called Eleventh Hour in 1974. Strangely for a song so strongly associated with female voices, their singer was actually male. LaBelle recorded it the following year and the rest is history.