سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 19
The Book of Purification
What To Say When Entering Al-Khala' (The Toilet)
أَخْبَرَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ أَنْبَأَنَا إِسْمَاعِيلُ، عَنْ عَبْدِ الْعَزِيزِ بْنِ صُهَيْبٍ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا دَخَلَ الْخَلاَءَ قَالَ اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْخُبُثِ وَالْخَبَائِثِ .
It was narrated that Anas bin Malik said: "The Messenger of Allah (ﷺ) entered Al-Khala' (the toilet) and said: 'Allahumma inni a'uthu bika min al-khubuthi wal-khaba'ith (O Allah, I seek refuge with You from male and female devils)."[1] [1] See Ma'alam As-Sunan by Al-Khattabi. And Al-Khala' is the area one relieves oneself in. It refers to outside or other than that, it should not be understood to mean toilet only.
Sunan an-Nasa'i, 19Sahih (Darussalam)