مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 358
Purification
How to act when relieving oneself - Section 2
وَعَنْ عَلِيٍّ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «سَتْرُ مَا بَيْنَ أَعْيُنِ الْجِنِّ وَعَوْرَاتِ بَنِي آدَمَ إِذَا دَخَلَ أَحَدُهُمُ الْخَلَاءَ أَنْ يَقُولَ بِسْمِ اللَّهِ» . رَوَاهُ التِّرْمِذِيُّ وَقَالَ: هَذَا حَدِيثٌ غَرِيبٌ وَإِسْنَاده لَيْسَ بِقَوي
‘Ali reported God’s messenger as saying, "The covering between the eyes of the jinn and the private parts of the children of Adam when one of them enters the privy is provided by his saying, ‘In the name of God.’” Tirmidhi transmitted it, saying that this is a gharib tradition and that its isnad is not strong.
Mishkat al-Masabih, 358صَحِيح لغيره (الألباني)