Sayyiduna Uthman Ghani (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) sent a delegation to Yemen and appointed as their leader one of them who was younger than the others. Some days passed, but they did not set out. The Prophet (peace and blessings be upon him) met one of them and said: "O so-and-so, what is the reason you have not gone?" He said: "O Messenger of Allah, our leader has been complaining of pain in his leg." The Prophet (peace and blessings be upon him) came to that leader, blew over him with a ruqyah and recited this: "In the name of Allah, seeking blessing, and with the help of Allah, I seek refuge in the might of Allah and His power from the evil of what is in it." He recited these words seven times, and the man was cured. That elderly man said to the Prophet (peace and blessings be upon him): "O Messenger of Allah, are you appointing him as our leader, when he is the youngest of us all?" The Prophet (peace and blessings be upon him) mentioned his being a scholar of the Qur'an. That elderly man said: "O Messenger of Allah, if I did not have this fear of Allah Almighty that, despite learning it, I would keep sleeping and would not be able to recite it while standing in prayer, I too would learn it." The Prophet (peace and blessings be upon him) said to that man: "Learn it! For the example of the Qur'an is like a leather bag which you fill with musk and tie up its mouth: if you open it, the fragrance of the musk will spread, and if you leave it, the musk is still kept there. Such is the example of the Qur'an: whether you recite it or it is in your breast (both cases are good)."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Yahya bin Salamah bin Kuhayl, whom the majority declared da'if (weak), while Ibn Hibban called him thiqah (trustworthy) and said: The hadiths his son transmitted from him are munkar (objectionable). (Allamah al-Haythami says:) I say: This is not one of the reports that his son transmitted from him.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب التفسير / 11642