It was narrated that Anas bin Malik said:
"Whenever the Messenger of Allah entered the toilet, he would say: 'A'udhu Billahi minal-khubthi wa'l-khaba'ith (I seek refuge with Allah from male and female devils).'" (FR)
English reference (FR): Vol. 1, Book 1, Hadith 298 (FR)
Arabic reference (FR): Book 1, Hadith 315 (FR)