A man was supplicating with two fingers, so the Messenger of Allah ﷺ said, "One, only One."In another wording, the Prophet ﷺ saw a man supplicating with both his fingers, so he forbade him and said, "With one of them, the right one."
أن رجلا كان يدعو بإصبعيه فقال رسول الله ﷺ: أحد أحد. وفي لفظ: أن النبي ﷺ أبصر رجلا يدعو بأصبعيه جميعا فنهاه وقال: بإحداهما باليمني.
It was narrated by Tirmidhi (3557), Nasai (1272), Ahmad (10739), and Hakim (1/536), all from the hadith of Safwan bin Isa, who said, Muhammad bin Ajlan narrated to us, from Qaqa bin Hakeem, from Abu Salih, from Abu Hurairah, and he related it with the first wording. Its chain is hasan because of Muhammad bin Ajlan, for he is hasan al-hadith. Tirmidhi said, "This is a hasan gharib hadith." Hakim graded its chain sahih.As for the second wording, it was narrated by Ibn Hibban (884) through the route of Abdullah bin Umar bin Aban, Hafs bin Ghiyath narrated to us, from Hisham, from Ibn Sirin, from Abu Hurairah, and he related it. Its chain is hasan because of Abdullah bin Umar bin Aban, who is Abdullah bin Umar bin Muhammad bin Aban, for he is hasan al-hadith.Tirmidhi said, "The meaning of this hadith about pointing with his two fingers in supplication at the testimony is that he should point with only one finger." His saying "Ahad, ahad" originally was "Wahid, wahid," from tawhid, but the waw was changed into a hamza. That is, point with one finger, because the One you are calling upon is one, having no partner.This companion whom the Prophet ﷺ saw is Saad bin Abu Waqqas, as mentioned in the hadith that follows.