When Bodhidharma was selected as the haeres by the twenty-seventh Patriarch Prajnatrar, he was told, "I wish you could transmit Buddhism to China after I passing away 60 years." So Bodhidarma reached Guanzhou from India by sea in the reign of Emperor Wu of Liang who was a fervent Buddhist sent official to invite Bodhidharma to his palace in capital city Jinling(now Nanjing).
Emperor Wu asked Bodhidharma, "Since I established the Liang Dynasty, I have built Buddhist temples, have translated and copied sutras and have persuaded countless people receiving Buddhist precepts, how much karmic merit have I earned?"
Bodhidharma replied,"None."
Emperor Wu asked,"Why is that?"
Bodhidharma said,"Good deeds had done with worldly intent bring good karma, but no merit."
However, Emperor Wu didn't realize the truth of Bodhidharma's words, who felt that the talk was not very congenial and travelled to the northern Chinese Kingdom of Wei. It is said that Emperor Wu regretted his having let Bodhidharma leave and dispatched his man rode fast horse to chase after Bodhidharma trying to beg him return. By the Yangtze River, the man saw Bodhidharma standing on a piece of reed floated away. That's the famous allusion "Crossing River By Reed". He came to Shaolin Monastery in Mount Song and faced a wall for nine years, not speaking for the entire time in a cave on the Wuru Peak of Shaoshi Mountain. Now the cave is called Damo Cave. Bodhidharma is revered as the Fist Patriarch of Chinese Chan Buddhism and Shaolin Monastery is regarded as the Ancestral Temple of Chan Buddhism.(Essay: Liu Tao   Chinese Zen Buddhism)