Majma al-Zawaid — Hadith 2796

It is reported from Ibn Ishaq that he said: He narrated to me how the Prophet (peace and blessings be upon him), in the middle of the prayer and at its end, would spread his left thigh, sit on his left hip, place his left hand on his left thigh, keep his right foot upright, and place his right hand on his right thigh; then, pointing with his index finger, he would affirm the Oneness of his Lord. Imran bin Abi Anas belongs to Banu Amir bin Lu'ayy, and he is thiqah (trustworthy); he narrated from Abu al-Qasim Miqsam, the freed slave of Abdullah bin al-Harith bin Nawfal, who said: A man from the people of Madinah narrated this hadith to me; he said: I prayed in the mosque of Banu Ghifar. During the prayer, when I sat, I spread out my left leg and sat on it, placed my left hand on my left thigh, kept the front part of my right foot upright, placed my right hand on my right thigh, and then pointed with my finger. (Here the word "foot" is used in the Arabic.) He said: Sayyiduna Khufaf bin Ima' bin Rahadah (may Allah be pleased with him), who had the honour of being a Companion of the Prophet (peace and blessings be upon him), saw me doing this. When I finished my prayer, he said: "O my son, why did you raise your finger?" I said to him: "I saw people doing this." He said: "You did right. The Prophet (peace and blessings be upon him) also used to do this. The polytheists used to say: 'Muhammad (peace and blessings be upon him) performs magic with this finger,' but they lied, for the Prophet (peace and blessings be upon him) did this in order to express the Oneness of his Lord by it."
Imam Ahmad recorded it, and Imam Abu Ya'la recorded something similar; he named the unnamed man as al-Harith, but I have not found anyone who gave his biography, and Imam Ahmad did not name him.