Sahih Al Bukhari Hadith Number 1930

Narrated `Aisha: (At times) in Ramadan the Prophet (peace be upon him) used to take a bath in the morning not because of a wet dream and would continue his fast.

30  Fasting
Hadith number 1930
Volume no 3
Chapter: 25 (Taking a bath by a person observing Saum (fast)