四分律刪繁補闕行事鈔 3.126

3.126

一制意者。良由眾生報力不同，上中下別。若上達之徒，身力資彊，制令分衛；隨緣少欲，得濟形命，志存道業，不假儲畜。中下之流，情同上士，而力劣不堪，必須資具，方能進策。是以大聖慈憫，因困餓死，方開結之，同界別處。釋淨名者，以飲食繁穢，同處生患，今既別結，情無儲畜，食不生罪，故名為淨；若同處長貪，違教受業，業是穢因，名不淨也。此從緣說淨，非對穢以明也。

First, the intention of the prohibition: This is truly because the retributive capacities of sentient beings differ, having superior, middling, and inferior grades. For those of superior attainment, their physical strength is robust, and they are enjoined to practice piṇḍapāta; conforming to circumstances with few desires, they can sustain their bodies and lives, fixing their minds on the work of the Path without relying on stored provisions. As for those of middling and inferior grade, their aspirations are the same as those of superior persons, yet their strength is feeble and inadequate; only with provisions can they spur themselves forward. Therefore, out of compassion, because [monks] were distressed and starving to death, the Great Sage first opened the demarcation of such grounds, in a separate place within the same boundary. Explaining the name 'pure': because food and drink are troublesome and impure, and keeping them in the same place gives rise to faults, now that a separate boundary is demarcated, the mind has no storage, and the food causes no offense; hence it is called 'pure.' If in the same place one fosters greed, violates the teaching, and receives karmic effects, karmic action is a defiled cause, and it is called 'impure.' This explains 'pure' from the standpoint of conditions, not in contrast to defilement.