Musnad Ahmad 32:543

Hassan narrated to us, Ibn Lahi'ah narrated to us, Bakr ibn Sawadah narrated to us, from Wafa' al-Khawlani, from Anas ibn Malik, who said: While we were reading—and among us were the Arab and the non-Arab, and the black and the white—the Messenger of Allah, peace and blessings of Allah be upon him, came out to us and said: "You are in goodness; you read the Book of Allah, and the Messenger of Allah, peace and blessings of Allah be upon him, is among you. And a time will come upon the people when they will straighten it [the Quran] just as they straighten an arrow shaft; they will hasten their rewards and will not delay them."