The Supreme Consciousness (which is known to reside in 20th dimension or even higher!), also referred to as the Primordial Buddha, created the Grand Cosmos and all the beings with it. As we go down the dimensional hierarchy, this energy of the Supreme Consciousness is divided further and further into spirits and then into individual souls. So from One Energy of the Supreme Consciousness is created so many souls. Ultimately the energy/consciousness of each soul is a part of the same source energy, the Supreme Consciousness. And hence in the highest sense we are all ONE. We are a part of one single Consciousness. That’s why ONENESS is the ultimate truth and one of the Highest virtues. You are a part of the One. You are one with the One. And realizing that you are one with the One is Enlightenment.
Like you are one with the One, each of the other souls is also one with the One. And hence , in essence a part of yourself. So when you harm the other, physically, mentally, emotionally, financially or spiritually, in the highest sense you harm yourself.
Understanding and practice of Oneness helps you to climb up the spiritual ladder. The more you practice separation/division, more you separate from the Supreme Consciousness and go lower down the spiritual ladder.
It’s like you are the Supreme Consciousness. Your chakras are the higher spirits and your body parts are the individual souls. If one hand harms the other hand, the entire you suffers!