摩訶止觀 2.37

2.37

Fourth, the samādhi of neither walking nor sitting. The preceding ones exclusively utilized walking or sitting; since this differs from the preceding ones, to complete the four propositions, it is named 'neither walking nor sitting'. In reality, it runs through walking, sitting, and all activities. Master Nanyue called it 'following one's own intent': as soon as a mental intention arises, one cultivates samādhi. The Large Sutra calls it 'the samādhi of awakening to mental states'; wherever the mind directs itself, one is consciously aware and clearly discerning. Although there are three names, they are in truth a single practice. Now, I explain the name in accordance with the sūtra. 'Awakening' means illuminating and discerning; 'mental state' means mental factors; 'samādhi' is as explained before. When a mental factor arises in the practitioner, one reflects and contemplates it, seeing no movement, root source, end, place of coming, or place of going; hence it is called 'awakening to mental states'.