妙法蓮華經玄義 6.72

6.72

今經顯六根互用，將三根足二百，向三根而互用耳。自在無礙能等，如《正法華》說。能縮，如身眼鼻之八百；能盈，如耳舌意千二百。經云：「若能持是經，功德則無量，如虛空無邊，其福不可限。」互用之意彰矣！

The present sūtra reveals the interchangeable function of the six faculties, bringing the three faculties to add two hundred toward the interchangeable function of the [other] three faculties. Free and unobstructed, they can be equal, as the Zheng fahua explains; they can contract, as in the eight hundred of the body, eye, and nose; they can expand, as in the one thousand two hundred of the ear, tongue, and mind. The sūtra says: 'If one can uphold this sūtra, one's merits will be immeasurable, like empty space without boundary, and its blessings cannot be limited.' The meaning of interchangeable function is thus made clear!