The word Sufi, or Saf, implies purity, which contains two qualities. That is pure which is unmixed with any element other than its own, or in other words, that is pure which existed in its own element unalloyed and unstained. And secondly, that is pure which is most adaptable. Pure water, for instance, is water without the mixture of anything else, and the test of its purity is that it can adapt itself to whatever is mixed with it. If it is mixed with a red powder it becomes red, if with a green powder, green.