Musnad Ahmad 1013:68

Hassan narrated to us, Ibn Lahi'ah narrated to us, Bakr ibn Sawadah narrated to us, from Wafa ibn Shurayh al-Sadafi, from Sahl ibn Sa'd, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Among you is the Book of Allah; the black, the red, and the white learn it. Learn it before a time comes when people will learn it, but it will not pass beyond their collarbones. They will straighten it as an arrow is straightened, so they will hasten its reward and not delay it."