Abu Hurairah r.a reported: Allah's Messenger s.a.w said, "Be prompt in doing good deeds (before you are overtaken) by turbulence which would be like a part of the dark night. A man would be a believer in the morning and turn to disbelief in the evening, or he would be a believer in the evening and turn to disbelief in the morning, and would sell his Faith for worldly goods. "

(muslim)