أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ بُكَيْرٍ، عَنْ نَابِلٍ، صَاحِبِ الْعَبَاءِ عَنِ ابْنِ عُمَرَ، عَنْ صُهَيْبٍ، صَاحِبِ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ مَرَرْتُ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم وَهُوَ يُصَلِّي فَسَلَّمْتُ عَلَيْهِ فَرَدَّ عَلَىَّ إِشَارَةً وَلاَ أَعْلَمُ إِلاَّ أَنَّهُ قَالَ بِإِصْبَعِهِ .
It was narrated that Suhaib, the Companion of the Messenger of Allah (PBUH) said: "I passed by the Messenger of Allah (PBUH) when he was praying, and greeted him with Salam. He returned my greeting with a gesture, or maybe it was just with his finger." Translation Not Available
Book Ref: Sunan An Nisai Book 13 Hadith 1186
Web Ref: Sunan An Nisai Vol 2 Book 13 Hadith 1187