Sunan An-Nasa'i - سنن النسائي
13. The Book of Forgetfulness (In Prayer) - كتاب السهو
37) Chapter: The prohibition of pointing with two fingers and with which finger one should point
It was narrated from Sa'd who said:
"The Messenger of Allah (ﷺ) passed by m when I was supplicating with my fingers and he said: 'Make it one, make it one' and pointed with his forefinger."
37) باب النَّهْىِ عَنِ الإِشَارَةِ، بِأُصْبُعَيْنِ وَبِأَىِّ أُصْبُعٍ يُشِيرُ
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ الْمُخَرِّمِيُّ، قَالَ حَدَّثَنَا أَبُو مُعَاوِيَةَ، قَالَ حَدَّثَنَا الأَعْمَشُ، عَنْ أَبِي صَالِحٍ، عَنْ سَعْدٍ، قَالَ مَرَّ عَلَىَّ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَنَا أَدْعُو بِأَصَابِعِي فَقَالَ . وَأَشَارَ بِالسَّبَّابَةِ . " أَحِّدْ أَحِّدْ "