I was thinking it was Gladys Knight and the Pips, but out of the two acts mentioned it would have been Marvin Gaye who made the song popular. THE definitive version.
It was Martha Reeves who did the original version, although Marvin's is the most famous & it's the arrangement on his version that people would usually cover since.
i really like both Marvin's version, and the extended rockier version by Creedence Clearwater Revival, i know this doesn't add to the above answers, but its not often you get CCR mentioned!