Narrated Anas: The Prophet (ﷺ) used to say when he entered the toilet:

بِسْمِ اللَّهِ، اَللَّهُمَّ إِنِّي أَعُوْذُ بِكَ مِنَ الْخُبُثِ وَالْخَبَائِثِ

Bismillaah, Allaahumma 'innee 'A'oodhu bika minal-khubuthi walkhabaa'ith

In the Name of Allah. O Allah, I seek protection in You from the male and female unclean spirits. Ali (RA) said, Rasoolullah (ﷺ) said: When one of you goes to a secluded place by the call of nature, the covering of the genitals of the children of Adam from the eyes of the jinn is to say "Bismillah".

Reference: Bukhari: 142