The whole teaching of Vedanta stands for one thing - that is love. Five hundred years before the advent of Jesus the Christ, Buddha taught: 'Hatred is never cured by hatred, but by love. This is the everlasting ethical law.'
And what is love? Love means expression of oneness.
Jesus the Christ said: 'Love thy neighbour as thyself.' But Jesus did not explain why we should love our neighbours as ourselves. That explanation you will find in Vedas, in the Vedanta philosophy, in the Upanishad. The Upanishad, which are the earliest writings of this universal philosophy, teach that we should love our neighbours as ourselves, not because they have done us some good or been kind to us, but even if they have spoken unkind words, even if they have taken wicked steps against us, even if they are spiteful and jealous of us, still we should love them because we are one with our neighbours in spirit.
There is only One Spirit. The apparent man seems to be different and separated from that Universal Spirit, which we regard as the Absolute, the Infinite Being, the Brahman. This Universal Spirit is abiding in us all, and we are like so many mirros which hold the image of the Divinity which is universal and one.
We are like grains of sand, even smaller, when we compare our physical bodies with the universe. Yet in these infinitesimally small particles of human bodies we find the reflection of the divine and self-effulgent sun of the universe. That is the image of God in man. But as the image of the sun cannot exist independent of the sun, so the human soul, which is the image of divinity, cannot exist, even for a second, independent of the divine sun, the divine being, whose reflection it is. We are all one in that Infinite Being, the Supreme Spirit, God, the Absolute, the Brahman, the Heavenly Father, the Divine Mother. The name vary, but the ideal is one.
... standing on that point of oneness, we should renounce everything that makes us feel as separate individuals, as independent of each other, as differentiated from each other. We should try to combine them all into that one harmonious whole. God is the One stupendous Whole of which we are but parts. And that is the truth.
- Thought on Philosophy and Religion by Swami Abhedananda