Narrated Ibn Abbas (RA):

Allah's Messenger (ﷺ) ordered a man to put his hand on his mouth when he came to the fifth pronouncement and said, "It would be the deciding one." [Reported by Abu Dawud and an-Nasa'i. It's narrators are reliable].

وَعَنِ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا; { أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-أَمَرَ رَجُلاً أَنْ يَضَعَ يَدَهُ عِنْدَ اَلْخَامِسَةِ عَلَى فِيهِ, وَقَالَ:

إِنَّهَا مُوجِبَةٌ

} رَوَاهُ أَبُو دَاوُدَ, وَالنَّسَائِيُّ, وَرِجَالُهُ ثِقَات ٌ [1]‏ .‏