Musnad Ahmad 1126:1

Hassan narrated to us, Ibn Lahi'ah narrated to us, Hibban bin Wasi' narrated to us, from his father, from Sa'd bin al-Mundhir al-Ansari, that he said: "O Messenger of Allah, shall I recite the Quran in three [days]?" He said: "Yes." And he used to recite it [in that manner] until he passed away.