The 'kill the Buddha' comment must be interpreted within the context of the nondual realization espoused by Zen Buddhism. Buddha-nature transcends categories, making room for a world of distinct objects that are also empty of inherent existence. Indeed, from the point of view of Buddha (awakeness) there is no inside or outside - only a creative display infused with unborn awareness. Within the rubric of Zen practice it is impossible to see the Buddha. It is possible to see things that have a 'buddha' signifier attached to them from the conventional point of view, but this would not be construed as an enlightenment experience. Your basic nature is Buddha, neither inside nor outside.
A special transmission outside the scriptures,
Not founded upon words and letters.
By pointing directly to one's mind,
It lets one see into own nature and attain Buddhahood.
From the Zen perspective, scriptures are nothing but scraps of paper for wiping up filth.
- Tokusan Hisamatsu
For the realisation of Zen, practice is absolutely necessary.
SOURCE: Zen and Sutras
These three are your greatest treasures.
Simple in actions and thoughts, you return to the source of being.
Patient with both friends and enemies,
you accord with the way things are.
Compassionate toward yourself,
you reconcile all beings in the world.”
SOURCE: Lao Tzu, Tao Te Ching
So when you practice zazen, your mind should be concentrated on your breathing. This kind of activity is the fundamental activity of the universal being. Without this experience, this practice, it is impossible to attain absolute freedom.
If you want to express yourself, your true nature, there should be some natural and appropriate way of expression. Even swaying right and left as you sit down or get up from zazen is an expression of yourself. It is not preparation for practice, or relaxation after practice; it is part of the practice. So we should not do it as if it were preparing for something else. This should be true in your everyday life. To cook, or to fix some food, is not preparation, according to Dogen; it is practice. To cook is not just to prepare food for someone or for yourself; it is to express your sincerity. So when you cook you should express yourself in your activity in the kitchen. You should allow yourself plenty of time; you should work on it with nothing in your mind, and without expecting anything. You should just cook! That is also an expression of our sincerity, a part of our practice. It is necessary to sit in zazen, in this way, but sitting is not our only way. Whatever you do, it should be an expression of the same deep activity. We should appreciate what we are doing. There is no preparation for something else.
A man traveling across a field encountered a tiger. He fled, the tiger after him. Coming to a precipice, he caught hold of the root of a wild vine and swung himself down over the edge. The tiger sniffed at him from above. Trembling, the man looked down to where, far below, another tiger was waiting to eat him. Only the vine sustained him.
Two mice, one white and one black, little by little started to gnaw away the vine. The man saw a luscious strawberry near him. Grasping the vine with one hand, he plucked the strawberry with the other. How sweet it tasted!
SOURCE: Zen Koans (parable)
“The concept, often described in English as “nondualism,” is extremely hard for the mind to grasp or visualize, since the mind engages constantly in the making of distinctions and nondualism represents the rejection or transcendence of all distinctions.”
The path that takes you to nirvana is rooted in desire — in skillful desires. This means that wisdom has to learn how to strategize, too, to strengthen skillful desires so that less skillful desires will listen to them.SOURCE "Pushing the Limits: Desire & Imagination in the Buddhist Path", by Thanissaro Bhikkhu
Now that title might seem a bit shocking, but think about this for a moment: An egoistic person will never really feel happy, so if you strive for your own happiness, that is an impossible goal, but you can make someone happy even if for a moment. So we are the source of our one another's happiness, but not of our own.