(13) Marriage
كتاب النكاح
(14c) Chapter: Invoking Curses - Section 3
(14) باب اللعان - الفصل الثالث
Mishkat al-Masabih 3322 
Ibn ‘Abbas said that when the Prophet ordered a man and wife to invoke curses regarding one another, he ordered a man to put his hand on his mouth when he came to the fifth utterance, saying that it would be the deciding one. Nasa’i transmitted it.
وَعَنِ ابْنِ عَبَّاسٍ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَمَرَ رَجُلًا حِينَ أَمَرَ الْمُتَلَاعِنَيْنِ أَنْ يَتَلَاعَنَا أَنْ يَضَعَ يَدَهُ عِنْدَ الْخَامِسَةِ عَلَى فِيهِ وَقَالَ: «إِنَّهَا مُوجِبَةٌ» . رَوَاهُ النَّسَائِيُّ
 لم تتمّ دراسته  (الألباني)حكم :
Reference : Mishkat al-Masabih 3322
In-book reference : Book 13, Hadith 236