[Lal]

Thanks, SengKiat.

Here is another link (it is the first paragraph there):
Peṭakopadesa: 5. Hāra­vibhaṅ­ga­pañca­ma­bhūmi

Petakopadesa is one of only three surviving original commentaries; they are included in the Tipitaka. To compare, Visuddhimagga was written around 450 CE, about 700 years later.