In the Masnavi, Rumi uses the whitening of the black slave's face by the Prophet Muhammad as a powerful metaphor for spiritual illumination, divine grace, and the radical transformation of the soul. The transition from black to white represents the purification of the heart ($qalb$) from spiritual darkness to the light of faith ($iman$). Rumi contrasts this profound transformation with the ignorance of the slave's master in the subsequent section, who fails to recognize him because he remains blind to inner realities and is trapped in the perception of outer, physical forms. This story underscores a core Sufi theme: that true identity is defined by the spiritual essence, not the physical body or societal status.