In Book Three of the Masnavi, Jalaluddin Rumi uses the story of Bilal ibn Rabah, the Prophet's muezzin, to emphasize the primacy of inner sincerity over outward formal correctness. When others complain that Bilal mispronounces the Arabic word 'hayya' as 'hay' during the call to prayer, the Prophet defends him, revealing that God prefers Bilal's heartfelt 'error' to the hypocrites' outwardly perfect pronunciation. This narrative serves as a central metaphor in Rumi's work, asserting that the spiritual weight of devotion is measured by love and purity of intent rather than strict adherence to linguistic or ritualistic forms.