RFI: sample in Royce da 5'9"'s "Heartbeat".

This may sound like a stupid question, but what song does Royce da 5'9"'s "Heartbeat" sample? The sampled lyrics go "listen to my heartbeat...", and it sounds like an old soul tune. I think it's been sampled before, and I've heard the original as well, but I can't remember who is it by. There are kazillion songs called "Heartbeat", I'm not sure which one it is.