The Prophet ﷺ passed by me while I was supplicating with two fingers, so he said, "One, one," and pointed with his index finger.
مر علي النبي ﷺ وأنا أدعو بإصبعي فقال: أحد، أحد وأشار بالسبابة.
Reported by Abu Dawud (1499) and Nasai (1273), and Hakim graded it sahih (1/536), all of them via Abu Muawiya, who said, Amash narrated to us, from Abu Salih, from Saad bin Abu Waqqas, and he related it. Its chain is sahih. There has been disagreement over it regarding Amash, but Abu Muawiya's version is closer to being correct, as Daraqutni said in Al-Ilal (4/397).Hakim said, "It is sahih according to the criteria of both of them, if Abu Salih Samman heard it from Saad." I say, there is no basis for Hakim's doubt about Abu Salih hearing from Saad, for he was born during the caliphate of Umar, and Saad bin Abu Waqqas died in the year fifty-five according to the well-known account. It has also been established that Abu Salih Zakwan asked Saad a question concerning zakat, and Bukhari stated explicitly in Tarikh al-Kabir (8/513) that he heard from Saad. And Allah knows best.