Narrated Suhayb:

I passed by the Messenger of Allah (ﷺ) who was praying. I saluted him and he returned it by making a sign. The narrator said: I do not know but that he said: He made a sign with his finger. This is the version reported by Qutaybah.

حَدَّثَنَا يَزِيدُ بْنُ خَالِدِ بْنِ مَوْهَبٍ، وَقُتَيْبَةُ بْنُ سَعِيدٍ، أَنَّ اللَّيْثَ، حَدَّثَهُمْ عَنْ بُكَيْرٍ، عَنْ نَابِلٍ، صَاحِبِ الْعَبَاءِ عَنِ ابْنِ عُمَرَ، عَنْ صُهَيْبٍ، أَنَّهُ قَالَ مَرَرْتُ بِرَسُولِ اللَّهِ صلى الله عليه وسلم وَهُوَ يُصَلِّي فَسَلَّمْتُ عَلَيْهِ فَرَدَّ إِشَارَةً ‏.‏ قَالَ وَلاَ أَعْلَمُهُ إِلاَّ قَالَ إِشَارَةً بِأُصْبُعِهِ وَهَذَا لَفْظُ حَدِيثِ قُتَيْبَةَ ‏.‏