Musnad Ahmad 788:200

Mu'adh ibn Mu'adh narrated to us, he said: Sufyan ibn Sa'id narrated to us, from Hakim ibn Daylam, from Abu Burdah, from his father, who said: "The Jews used to come to the Prophet, peace and blessings of Allah be upon him, and sneeze in his presence, hoping that he would say to them: 'May Allah have mercy on you.' So he would say to them: 'May Allah guide you and rectify your affairs.'" *** Muhammad ibn al-Sabah narrated to us—'Abdullah said: And I heard it myself from Muhammad ibn al-Sabah—he said: Isma'il ibn Zakariyya narrated to us, from Burayd, from Abu Burdah, from Abu Musa, who said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Maintain the Quran, for it is more prone to escaping from the hearts of men than camels from their hobbles."