الأترجة
A fragrant citrus fruit used by the Prophet ﷺ as a simile for the believer who recites Qur'an, and discussed separately by commentators for its digestive properties.
مَثَلُ الْمُؤْمِنِ الَّذِي يَقْرَأُ الْقُرْآنَ كَمَثَلِ الْأُتْرُجَّةِ، رِيحُهَا طَيِّبٌ وَطَعْمُهَا طَيِّبٌ
“The believer who recites the Qur'an is like a citron: its scent is pleasant and its taste is pleasant.” (meaning, not a literal translation)
The full hadith continues with three further comparisons — the believer who doesn't recite Qur'an is like a date (good taste, no scent); the hypocrite who recites is like basil (pleasant scent, bitter taste); and the hypocrite who doesn't recite is like a bitter gourd (neither pleasant scent nor taste) — making this one of several linked similes rather than a standalone statement about citron specifically.
While this hadith is a spiritual simile rather than a medical instruction, Ibn al-Qayyim discusses citron separately in his medical chapters as beneficial for the heart, digestion, and as a moth-repellent for stored clothing. He describes different parts of the fruit serving different purposes in classical practice — the peel used for its aromatic and preservative qualities, the flesh and juice for digestive complaints, reflecting how thoroughly a single fruit could be used across the classical medical tradition.
Citron and citrus peel extracts have been studied in modern research for compounds with antioxidant and mild antimicrobial activity, and citrus fruits broadly are well established as a vitamin C source. Noted here as separate modern context, not a validation of the hadith's spiritual meaning, which is about the believer's character, not the fruit's chemistry.