حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، عَنْ مَنْصُورٍ، عَنْ ذَرٍّ، عَنْ يُسَيْعٍ الْحَضْرَمِيِّ، عَنِ النُّعْمَانِ بْنِ بَشِيرٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏"‏ الدُّعَاءُ هُوَ الْعِبَادَةُ ‏{‏ قَالَ رَبُّكُمُ ادْعُونِي أَسْتَجِبْ لَكُمْ ‏}‏ ‏"‏ ‏.‏
Translation
Narrated Sa'd ibn AbuWaqqas

The Prophet (ﷺ) passed by me while I was supplicating by pointing with two fingers of mine. He said: Point with one finger; point with one finger. He then himself pointed with the forefinger.