法華義疏 2.78

2.78

Illuminating while constantly still is called concentration; still while constantly illuminating is called wisdom. When wisdom is expressed externally, it is called a sūtra; when stillness reaches its utmost internally, it is called concentration. 'Unmoving in body and mind' concludes the above two meanings. By the body being unmoving, it concludes the above uprightness of the body; by the mind being unmoving, it concludes the above stillness of the mind. The ultimate person realizes the true aspect and yet possesses body and mind; though having a body, it is not an ordinary body, and the body is unmoving; though having a mind, it is not an ordinary mind, and the mind is unmoving; therefore the body is like withered wood and the mind is like dead ashes. Furthermore, the body and mind being unmoving reveals that the time of the Buddha's arising from concentration is not predetermined, giving rise to the subsequent doubts and questions.