From Sahih Muslim (Hadith 313):
It is narrated on the authority of Abu Huraira that the Messenger of Allah (ﷺ) observed:Be prompt in doing good deeds (before you are overtaken) by turbulence which would be like a part of the dark night. During (that stormy period) a man would be a Muslim in the morning and an unbeliever in the evening or he would be a believer in the evening and an unbeliever in the morning, and would sell his faith for worldly goods
Reference: Muslim 313