Hadith Bukhari,Book 98, Hadith 7655

حَدَّثَنَا هُدْبَةُ بْنُ خَالِدٍ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، حَدَّثَنَا أَنَسٌ، عَنْ أَبِي مُوسَى ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ مَثَلُ الْمُؤْمِنِ الَّذِي يَقْرَأُ الْقُرْآنَ كَالأُتْرُجَّةِ، طَعْمُهَا طَيِّبٌ وَرِيحُهَا طَيِّبٌ، وَالَّذِي لاَ يَقْرَأُ كَالتَّمْرَةِ، طَعْمُهَا طَيِّبٌ وَلاَ رِيحَ لَهَا، وَمَثَلُ الْفَاجِرِ الَّذِي يَقْرَأُ الْقُرْآنَ كَمَثَلِ الرَّيْحَانَةِ، رِيحُهَا طَيِّبٌ وَطَعْمُهَا مُرٌّ، وَمَثَلُ الْفَاجِرِ الَّذِي لاَ يَقْرَأُ الْقُرْآنَ كَمَثَلِ الْحَنْظَلَةِ، طَعْمُهَا مُرٌّ وَلاَ رِيحَ لَهَا ‏" ‏‏

Narrated Abu Musa:
The Prophet said, 'The example of a believer who recites the Qur'an is that of a citron (a citrus fruit) which is good in taste and good in smell. And the believer who does not recite the Qur'an is like a date which has a good taste but no smell. And the example of an impious person who recites the Qur'an is that of Ar-Rihana (an aromatic plant) which smells good but is bitter in taste. And the example of an impious person who does not recite the Qur'an is that of a colocynth which is bitter in taste and has no smell."

 
English reference: Vol. 9, Book 93, Hadith 649

Arabic reference: Book 98, Hadith 7655