Musnad Ahmad 32:274

Yazid ibn Harun narrated to us, Humayd informed us, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not be amazed by anyone until you see how his life ends. For a person may perform good deeds for a period of his life, or for a span of his time, such that if he were to die upon them, he would enter Paradise. Then he changes and performs evil deeds. And a servant may perform evil deeds for a span of his time, such that if he were to die upon them, he would enter the Fire. Then he changes and performs good deeds. And if Allah intends good for a servant, He employs him before his death." They said: "O Messenger of Allah, how does He employ him?" He said: "He grants him success in performing a good deed, then He takes his soul upon it."