Hakuin Ekaku, also known as Hakuin Zenji, was a Japanese Zen master who lived from 1686 to 1769. He is considered to be the reviver of the Rinzai school of Zen Buddhism, and is known for his teachings and writings that have had a lasting impact on the practice of Zen.

One of Hakuin's most famous works is "The Song of Zazen," a poem that describes the practice of zazen, or seated meditation. This poem is significant for several reasons.

Firstly, "The Song of Zazen" is a clear and concise guide to the practice of zazen. In just 17 lines, Hakuin describes the physical posture, mental attitude, and ultimate goal of zazen. This poem has been used by Zen practitioners for centuries as a reminder of the essential aspects of the practice, and as a source of inspiration and guidance.

Secondly, "The Song of Zazen" emphasizes the importance of direct experience over intellectual understanding. Hakuin writes, "To understand the mystery of Zen / One must push aside words and letters." This highlights the Zen belief that enlightenment cannot be attained through studying scriptures or intellectualizing about it, but through direct experience and practice.

Another significant aspect of "The Song of Zazen" is its emphasis on the unity of body and mind. Hakuin writes, "Body and mind of themselves will drop away / And your original face will be manifest." This line speaks to the idea that in zazen, the body and mind are not separate entities, but rather one integrated whole. Through the practice of zazen, one can experience the true nature of the self.

Furthermore, "The Song of Zazen" emphasizes the importance of perseverance and determination in the practice of Zen. Hakuin writes, "If you wish to attain suchness / You must practice suchness without delay." This line reminds practitioners that enlightenment is not something that can be achieved overnight, but requires consistent effort and dedication.

Lastly, "The Song of Zazen" is significant because it reflects Hakuin's own personal experience and understanding of Zen. Hakuin was known for his intense and rigorous practice, and his teachings were based on his own direct experience of enlightenment. Therefore, this poem is not just a theoretical or intellectual exploration of Zen, but a reflection of Hakuin's own journey towards enlightenment.

In conclusion, "The Song of Zazen" is a significant work by Hakuin Ekaku that encapsulates the essential teachings and principles of Zen Buddhism. Its concise and poetic form makes it accessible and inspiring for practitioners of all levels, and its emphasis on direct experience and perseverance serves as a reminder of the true nature of Zen practice.