The old landlady named Osan of a teashop in front of the temple, where Hakuin Zenji lived, advised the monks who were attending the koan of "the sound of one hand clapping" during meditation in the temple, and said, "It would be better clapping both hands to sell goods rather than trying to hear the sound of a single hand". This time, let's to see the koan "Do your business clapping both hands."

Hakuin Ekaku (1686-1769), known as the ancestor who rejuvenated the Rinzai school in Japanese Zen Buddhism, taught us, "Two hands clap and there is a sound; what is the sound of one hand?" A clapping sound arises when one claps with both hands. However the sound vanishes in a twinkling of an eye and so does everything in this world. If one is seized by an instant phenomenon, which is a result of different factors that are either continually changing or being extinguished, he will be unable to see the truth. Only the one who can hear a sound before two hands clap, can see the truth. In other words, he who faces “the Self”, his intrinsic nature at a time before his parents were born, can see the truth.

The old landlady named Osan of a teashop in front of the temple, where Hakuin lived, insinuated itinerant priests who concentrated on the koan (subject which Zen-masters give each religious to learn and practice the doctrine of Buddhism) of "the sound of one hand clapping" during meditation in the temple, and said, "It would be better clapping both hands to sell goods rather than trying to hear the sound of a single hand". When Hakuin heard of this, he said, "If your business prospers by clapping your hands, you need not hear the sound of a single hand."

The discernment of the landlady, who proclaimed that doing one's business to get along in this world is the way for a single leap's entry to the kingdom of god, is incisive. Naagaarjuna (150?-250?) described this theory in his book "The Treatise on the Middle Way" and stated: "Dharmas (phenomena) are born of causes and conditions. I say they are thus empty. They are also called false and fictitious, and that is also the truth of the Middle Way." We can also find the same theory in the Heart Sutra as saying, "Form (phenomenon) is emptiness, emptiness is also form. Emptiness is no other than form, form is no other than emptiness"

　To the Jews who believed in him, Jesus said, “If you hold to my teaching, you are really my disciples. Then you will know the truth, and the truth will set you free.”(John 8:31-32)

A rosy youth in the morning may become crumbling bones in the evening. Life is too uncertain. Why do we endlessly suffer fears or obstacles? Because it is too difficult to grasp and hold onto the truth in this world. Therefore Jesus might have taught us that if one saw his suffering in this world as a 'Genjo-koan' (Subjects which Zen masters give their students in the meditation hall are called 'Kosoku-koan' and the current problems faced by the people in the real world are called 'Genjo-koan') given by God and resolving this koan was the divine mandate from Heaven, in other words, kept Jesus' teaching to take up one's own cross and followed Jesus, he would be the one who lived in heaven while staying in this world. (Eko-an Hensho-koji：2008/11/16)

According to the dialectic of the Gospel of John,

How then can a man possess eternal life?

When he said, "You are Huichao," Zen Master Fayan thrusted vivid Self in Huichao in front of his eyes.