In Poem 21 of Chapter 12 of Attar's Mokhtar Nameh, the poet addresses the deeply ingrained and polluting nature of the ego (نفس, nafs). The poem asserts that a person's essence can become so saturated with egoism that even burning in fire for lifetimes cannot completely eradicate it. The metaphor of the 'scent of egoism' rising from one's ashes illustrates the profound difficulty of achieving true spiritual purity and complete self-effacement.