Abu Dawud
Purification (Kitab Al-Taharah)
Book Number: 001 / Hadith Number: 236
Narated By 'Aisha, Ummul Mu'minin : The Prophet (pbuh) was asked about a person who found moisture (on his body or clothes) but did not remember the sexual dream. He replied: He should take a bath. He was asked about a person who remembered that he had a sexual dream but did not find moisture. He replied: Bath is not necessary for him. Umm Salamah then asked: Is washing necessary for a woman if she sees that (in her dream)? He replied: Yes. Woman are counterpart of men.