The Visuddhimagga, written in Sri Lanka by Buddhaghosa in the fifth century, sets out the Buddhist path under the three trainings: two chapters on virtue, eleven on concentration and its forty subjects, and ten on wisdom, organized around seven purifications. It is the most authoritative work of the Theravāda outside the canon.
Visuddhimagga
The “Path of Purification”: Buddhaghosa’s fifth-century manual of the whole Theravāda path.
Also: Path of Purification