Abu Dawud Book 2, Hadith Number 1445.
Chapter : Encouragement to get up during the night.
Narated By Abu Hurairah : The Prophet (PBUH) said: May Allah show mercy to a man who gets up during the night and prays, who wakens his wife and she prays; if she refuses, he sprinkles water on her face. May Allah show mercy to a woman who gets up during the night and prays, who wakens her husband and he prays; if he refuses she sprinkles water on his face.