ben harper cover song?

my friend told me about a song Ben Harper sang once as a cover, but
for the life of me I can
t remember what it was. It was recorded, he had it on his iTunes but
deleted it and can't find it. I want to find it for him to show I was
listening to him but LOL i can't remember what it was. Have yoou ever
heard Ben Harper sing a cover song? any ideas? It was a fairly well
known, but older song.