Musnad Ahmad 32:1389

Muhammad ibn Abi ‘Adi narrated to us, from Humayd, who said: Anas said: "Do not be amazed by the deed of a man until you know what he will conclude his life with. For a man may perform an evil deed for a period of his time—or a duration of his life—such that if he were to die upon it, he would die upon evil, then he turns to a righteous deed and concludes his life with it. And a servant may perform a righteous deed for a period of his time—or a duration of his life—such that if he were to die upon it, he would die upon good, then he turns to an evil deed and concludes his life with it." He said: Humayd attributed it to the Prophet (raised it) once, then refrained from doing so afterward.