Sandokai

The Sandokai or 'Harmonious Song of Difference and Sameness' is a poem by the eighth Chinese Zen ancestor Shitou Xiqian and a fundamental text of the Soto school of Zen, chanted daily in temples throughout the world.

The text

The poem is about the interplay of darkness and light. The ultimate truth depends on both, and one cannot understand the nature of reality fully without acknowledging both aspects. On the other hand, the poem states "The spiritual source shines clear in the light;
the branching streams flow on in the dark" and "Refined and common speech come together in the dark, clear and murky phrases are distinguished in the light". So the light has a specific quality in this poem, which probably means insight in reality or the self is gained because of the light element.

Toward the end of his life Shunryu Suzuki Roshi gave a series of lectures on the Sandokai.