Blake's lines from The Everlasting Gospel, quoted as the conclusion of the whole teaching: if thou humblest thyself, thou humblest me; thou also dwellest in eternity; thou art a man, God is no more, thy own humanity learn to adore. Neville draws the consequence at once - black, red, yellow, there is only God and nothing but God - so the adoration owed to God is owed to the humanity in front of you, and humbling any man humbles God.