Sosan, also known as Sengcan, was a Chinese Zen teacher who is considered the Third Zen Patriarch in the Zen Buddhist tradition. Not much is known about his personal life and background, but there are some details that have been passed down through historical accounts and legends.

According to traditional accounts, Sosan was born in the 6th century in the city of Huiji, in what is now known as Zhejiang Province, China. He was born into a wealthy family and received a good education, studying Confucianism and Taoism. However, he became dissatisfied with these teachings and began searching for a deeper understanding of life.

Sosan is said to have encountered the teachings of the Second Zen Patriarch, Huike, and was deeply inspired by them. He became Huike's disciple and dedicated himself to the practice of Zen Buddhism.

There are also legends surrounding Sosan's life. One popular legend states that he was a skilled archer and was once challenged by a rival archer. Instead of competing, Sosan shot an arrow into the air and declared, "If you can hit my arrow, I will admit defeat." The rival archer was unable to hit the arrow, and Sosan declared that this was a metaphor for the elusive nature of enlightenment.

Another legend tells of Sosan's encounter with a young girl who was carrying a bucket of water. When the bucket broke, Sosan used his robe to carry the water and continued on his way. This act of kindness and selflessness is seen as a demonstration of Sosan's understanding of the interconnectedness of all beings.

Sosan is also believed to have spent some time in meditation at Mount Song, a sacred mountain in China. It was during this time that he is said to have written the famous poem "Xin Xin Ming" or "Verses on the Faith Mind." This poem is considered a key text in Zen Buddhism and is often used as a teaching tool for understanding the nature of reality and the path to enlightenment.

Sosan's teachings were passed down through his disciples, and he is credited with spreading the practice of Zen Buddhism throughout China. He is also believed to have played a role in the transmission of Zen to Korea and Japan.

In summary, while not much is known about Sosan's personal life and background, he is remembered as a devoted Zen practitioner and teacher who played a significant role in the development and spread of Zen Buddhism. His teachings continue to inspire and guide practitioners on the path to enlightenment.