It was narrated that 'Ali said:
"The Messenger of Allah said: 'The screen between the Jinn and the nakedness of the sons of Adam is that when a person enters the Kanif, he should say: Bismillah (in the name of Allah).'" (ID)
English reference (ID): Vol. 1, Book 1, Hadith 297 (ID)
Arabic reference (ID): Book 1, Hadith 314 (ID)