Sunan Ibn Majah, Hadith 967 ⓘ
It was narrated from Ka’b bin ‘Ujrah that the Messenger of Allah saw a man who had interlocked his fingers during the prayer, so the Messenger of Allah separated his fingers.
حَدَّثَنَا عَلْقَمَةُ بْنُ عَمْرٍو الدَّارِمِيُّ، حَدَّثَنَا أَبُو بَكْرِ بْنُ عَيَّاشٍ، عَنْ مُحَمَّدِ بْنِ عَجْلاَنَ، عَنْ سَعِيدٍ الْمَقْبُرِيِّ، عَنْ كَعْبِ بْنِ عُجْرَةَ، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ رَأَى رَجُلاً قَدْ شَبَّكَ أَصَابِعَهُ فِي الصَّلاَةِ فَفَرَّجَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ بَيْنَ أَصَابِعِهِ .
also referenced under: Book 5, Hadith 1020 (In-Book) & Volume 2, Book 5, Hadith 967 (DarusSalam)