The excerpts of this story is from yogichen.com
… When we say there is no practice in Chan, this means one has learned to box without fists. Just like a bird which flies through the sky but leaves no tracks. When you get the Chan function, then you can enter the world and say I have no need to renounce, but not before. It is possible to find the truth in each blade of grass, i.e., whorehouses, gambling casinos, theaters, and bars, etc. But it is best to keep a little distance at first to make your comprehension very sharp. When you come back every blade of grass will bow down to you.
Now I will tell you a story about the grass. When Bodhidharma returned to Tibet from China, Milarepas disciples wanted him to go meet Bodhidharma. Milarepa said that he was too old and did not want to. But the disciples insisted, so the two met, and their disciples requested some competition. They decided to see who could stand on a single blade of grass.
When Milarepa stood on the grass blade, it bent a little, but not so with Bodhidharma. It remained perfectly straight. The disciple asked why this had happened. Bodhidharma replied it is only because I was born in India, so the earth god supports me much more than supports your Guru. Our Chan comprehension must reach everywhere. Everything is “Wu” with the Chan. We must be able to stand up on each blade of grass. This means that we must be able to penetrate every sorrow and poison.