To enter by reason means to realize the essence through instruction and to believe that all living things share the same true nature, which isn't apparent because it's shrouded by sensation and delusion.
One clings to life although there is nothing to be called life; another clings to death although there is nothing to be called death. In reality, there is nothing to be born; consequently, there is nothing to perish.
All Buddhas preach emptiness. Why? Because they wish to crush the concrete ideas of the students. If a student even clings to an idea of emptiness, he betrays all Buddhas.
The mind's capacity is limitless, and its manifestations are inexhaustible. Seeing forms with your eyes, hearing sounds with your ears, smelling odors with your nose, tasting flavors with your tongue, every movement or state is all your mind.
Don't hate life and death or love life and death. Keep your every thought free of delusion, and in life you'll witness the beginning of nirvana, and in death you'll experience the assurance of no rebirth.
Externally keep yourself away from all relationships, and internally have no pantings in your heart; when your mind is like unto a straight-standing wall, you may enter into the Path.