Although the beat is originally Chic's, the Spank the Monkey sample is from
Grandmaster Flash -- The Adventures of Grandmaster Flash on the Wheels of Steel (yes that is the name of the song)
You can tell because of the scratching -- the Sugarhill Gang actually had Chic come in to play the beat for them -- no records or mixing was involved.
You can also tell because, right at the end, there's a drum beat from Michael Viner's Incredible Bongo Band -- Apache.