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."

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 ﷺ وَأَنَا أَدْعُو بِأَصَابِعِي فَقَالَ " أَحِّدْ أَحِّدْ " . وَأَشَارَ بِالسَّبَّابَةِ .