In the Sung Dynasty, Ch'ang-lu Tsung-tse 長蘆宗賾 wrote the Tso-ch'an i 坐禪儀, The Manual of tso-ch'an. In it, he said that a person who has just experienced Buddha-nature should continue to practice tso-ch'an. Then it is possible to become like the dragon who gains the water, and the tiger who enters the mountains. The dragon gaining the water returns to his ancestral home, and is free to dive as deep as he wishes. The tiger entering the mountain has no oppsition; he may ascend the heights and roam wherever he wills. So Ch'ang-lu is saying that practicing tso-ch'an after enlightenment enhances and deepens one's realization.

Yueh-shan Wei-yen 藥山惟嚴(745-828), an enlightened monk, was doing tso-ch'an. His master, Shih-t'ou asked him, "What are you doing tso-ch'an for?" Yueh-shan answered, "Not for anything." "That means you are sitting idly", Shih-t'ou continued. Yueh-shan said, "If this is idle sitting, then that would be for something." The master then said, "What is it that is not for anything?" The monk anwered, "A thousand sages won't know."

On the one hand, we say that persons who have had realization should do tso-ch'an to enhance their enlightenment; on the other hand, we say the enlightened person sits without purpose. What is the explanation? For the practitioner whose enlightenment is not deep, practice is necessary to deepen it; for one who is deeply enlightened, practice is just part of daily life.

One day, when Ch'ao-chou was already thoroughly enlightened and actively helping others, his tso-ch'an was interrupted by a visit from a prince. He did not rise from his seat, explaining himself with a verse:

Ever since youth I have foregone meat. This body is now old. When visitors come, I have no strength to rise from the Buddha-seat.