四分比丘戒本疏 2.130

2.130

四十七、污手捉飯器者，西方以手喫食，捉食之手名污手也。《五分》云「食手者，食污其手及肥膩也。」

Rule forty-seven, holding a food vessel with soiled hands: in the Western regions they eat food with the hands; the hand holding food is called a soiled hand. The Mahīśāsaka-vinaya says: "An eating hand is when food soils one's hand with grease and fat."