分別功德論 4.31

4.31

堅牢比丘者以常居山澤閑靜之處為行、難提比丘常以乞食耐辱為行、金毘羅比丘以七家乞食為行、施羅以一處食為行，十二頭陀各居一行。浮彌比丘者，守持三衣，不離食息。或曰造三衣者，以三轉法輪故；或云為三世；或云為三時故，故設三衣，冬則著重者、夏則著輕者、春秋著中者。為是三時故，便具三衣，重者五條、中者為七條、薄者十五條。若大寒時，重著三衣可以障之。或曰亦為蚊虻蟆子故設三衣。以是緣故常持不忘，故云第一。

Bhikṣu Dṛḍhapratijña made it his practice to dwell constantly in quiet and secluded places among mountains and marshes; Bhikṣu Nandi made it his practice constantly to beg for food and endure humiliation; Bhikṣu Kimbila made it his practice to beg food from seven households; and Śīla made it his practice to eat in one place—each of the twelve dhūtas maintaining one practice. As for Bhikṣu Bhūmi, he kept and maintained the three robes, not parting from them whether eating or resting. Some say that the creation of the three robes was on account of the three turnings of the wheel of the Dharma; some say it was on account of the three times (past, present, and future); and some say it was on account of the three seasons that the three robes were established: in winter one wears the heavy one, in summer one wears the light one, and in spring and autumn one wears the intermediate one. On account of these three seasons, he had the three robes complete: the heavy one had five strips, the intermediate one had seven strips, and the thin one had fifteen strips. In times of great cold, wearing the three robes layered over each other could ward it off. Some also say the three robes were established on account of mosquitoes, gnats, and sandflies. Because of these reasons, he constantly maintained them without neglecting them, and was therefore called foremost.