Once, a Chan master named Deshan had the secular surname Zhou, and his specialization in the study of the Diamond Sutra earned him the name Zhou Jingang (Diamond Zhou). One day, he heard of Chan Master Longtan’s (Dragon Lake) teaching: “Seeing one’s true nature is to become a buddha.” Diamond Zhou did not think this was a bad teaching, just that it was impossible, unfathomable, and too hard to believe. He believed that the cultivation of learning to realize buddhahood must take three incalculable great kalpas to succeed, so how can one become a buddha by just seeing one’s true nature? Hence, he set out to challenge Master Longtan.
While on his way, Diamond Zhou was getting hungry. Just at that moment, he saw a street stall with an old lady selling Chinese buns, so he walked over to buy some. When the old lady saw that Diamond Zhou was shouldering a heavy load of books and perspiring down his back, she wondered what inside could be so precious; so, she asked, “What are those books you carry?” Diamond Zhou replied, “What I carry is The Blue Dragon Commentary on the Diamond Sutra that I wrote myself.” Hearing this, the old lady said, “Since you are an expert on the Diamond Sutra, then allow me to ask you a question. If you can answer it, Venerable, I will make an offering of these buns to you. If not, I won’t sell you any, no matter how much money you want to give.” Diamond Zhou thought to himself, “I specialize in studying the Diamond Sutra, and you want to try and stump me with a test? You, old lady, really don’t know who you are talking to. What a joke!” The old lady then asked, “The Diamond Sutra says, ‘The mind of the past is ungraspable, the mind of the present is ungraspable, and the mind of the future is ungraspable.’ May I ask the Venerable, which mind is it that you are ordering [with]?” Diamond Zhou found himself unable to respond, completely dumbfounded by this unexpected defeat.
Good cultivators, if you were Diamond Zhou, could you answer this question? In fact, only an enlightened person can respond to it properly. Even if there are written annotations providing clear and logical explanations, they are only words and have nothing to do with [realizing] the nature of the mind. That is why Diamond Zhou was unable to respond. If Shifu were Diamond Zhou, simply, I would just pick up a bun and eat it. It’s that simple.
As night fell, Diamond Zhou finally found Master Longtan’s place. Seeing no one inside, he said, “It’s dark and I see neither lake nor dragon. Where is the Longtan (Dragon Lake)?” Master Longtan came out and replied, “You have already arrived at Longtan.” Since Diamond Zhou did not understand his meaning and it was already quite late, Master Longtan invited him to retire for the night. Lifting a curtain to leave, Diamond Zhou saw it was pitch black outside, so he stepped back in. Master Longtan was very kind and immediately lit a paper lantern for him to use. Just as Diamond Zhou was reaching out to take the lantern, however, the Master suddenly blew it out. At that moment, Diamond Zhou had a realization of enlightenment.
What is this realization? At first, nothing can be seen in the darkness, but with the light from a lit lantern, things are seen. When the lantern is blown out, nothing can be seen again. Light and darkness mutually dispel each other in a given space. Hence, the realization is that light and darkness are [dualistic], illusory phenomena; however, the mind that knows light and darkness is always present. With this realization, just keep the mind free of impurities—let it be clear, lucid, and in command wherever we go. This, then, is called the stage of cultivating the Way (修道位xiu-dao-wei).
Dharma Talk at Chan-7 Retreat for Monastics, 1996