From Zenwiki

(坐禅: sitting meditation) is the core practice of Buddhism, as he is usually represented in Zazen (sitting meditation). Sitting, especially in full cross-legged position called full lotus position, is the stable, solid posture to stay unmoved (physically and mentally) and wakeful unlike lying down (to decrease wakefulness to sleep) and moving (walking, running, etc., to specific movement to specific goal). This solid sitting, unmoved by anything, makes stilling karma most perfectly leading to nirvana, no-wind (of karma). Karma is the origin of sense organs and perception, then conception, emotion, volition, perceived world.

Sitting meditation allows one to see how these things originate and operate, and how our living/life originate and operate. Zazen allows one to trace back to the origin of our life and living as in [[the four stages of meditation]], to figure out the key of karma functioning there, and how to control it. Zazen is the key to still karma, see its significance, still its function, serve it for all, save all from it, and stop suffering of all.