大乘義章 19.32

19.32

三不護義，如經中說「如來三業純淨離過，不須防護，名三不護。」諸阿羅漢三業雖淨，常須防護方能離過；如來異彼，是故宣說三不護矣。問曰：如來何因緣故身口意業不須防護？久修淨戒性成就故，常住深定未曾出故，三業恒隨智慧行故，住大涅槃永寂滅故，是故三業不須防護。三不護義，辨之略爾。

The meaning of the three non-protections: as stated in the sūtra, 'The Tathāgata's three karmas are purely clean and free from fault, not needing to be guarded; hence they are termed the three non-protections.' Although the three karmas of arhats are pure, they must always guard them in order to be free from fault; the Tathāgata is different from them, and therefore the three non-protections are expounded. Question: For what reason do the Tathāgata's karmas of body, speech, and mind not need to be guarded? Because he has long cultivated pure precepts and his nature is perfected; because he always abides in deep samādhi and has never emerged; because his three karmas constantly follow the operation of wisdom; and because he abides in great nirvāṇa, permanently tranquil and extinguished; therefore, his three karmas do not need to be guarded. The meaning of the three non-protections is briefly discriminated like this.