Musnad Abu Ya'la al-Mawsili 160:120

And with his chain of narration, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Hasten to perform deeds before tribulations that are like pieces of the dark night. A man will wake up as a believer and reach the evening as a disbeliever, and he will reach the evening as a believer and wake up as a disbeliever, selling his religion for a small portion of the worldly life."