摩訶止觀 8.65

8.65

夫長病遠行是禪定大障。若身染疾，失所修福，起無量罪。經云：「破壞浮囊，發撤橋梁，忘失正念。」病故毀戒，如破浮囊；破禪定，如撤橋梁；起邪倒心，惜膿血臭身，破清淨法身，名「忘失正念」。為是義故，應觀病患境。復次，有人平健悠悠，徙倚懈怠；若病急時，更轉用心，能辦眾事。又機宜不同，悟應在病。即是四悉檀因緣，應須病患境也。

Chronic illness and long journeys are great obstacles to meditative absorption. If the body is afflicted with disease, one loses the merit one has cultivated and produces immeasurable wrongdoing. A sūtra says: "It punctures the floating raft, demolishes the bridge, and causes one to forget right mindfulness." Violating the precepts because of sickness is like puncturing the floating raft; destroying meditative absorption is like demolishing the bridge; giving rise to mistaken, inverted thoughts, cherishing this foul body of pus and blood, and ruining the pure dharmakāya is called "forgetting right mindfulness." For this reason, one should contemplate the realm of illness. Furthermore, some people are relaxed, idle, vacillating, and lazy when healthy and peaceful; but when illness becomes urgent, they turn their application of mind around and are able to accomplish many matters. Moreover, capacities and aptitudes vary, and for some, awakening should occur in the midst of illness. This is precisely the conditions of the four siddhāntas, whereby the realm of illness is necessary.