It is narrated from Abu al-Qasim Miqsam (may Allah have mercy on him): A man from the people of Madinah narrated to me: I prayed beside Khufaf bin Ima' bin Rahadah (may Allah be pleased with him). He saw me pointing with my finger in the prayer, and he said: O my nephew, why do you do this? I said: I have seen the righteous and the jurists doing it like this. He said: You have spoken rightly; I saw the Messenger of Allah (peace and blessings be upon him): when he sat for the tashahhud in the prayer, he would point with his finger. The polytheists would say: He is only casting magic on us. Whereas the Messenger of Allah (peace and blessings be upon him) intended tawhid (the Oneness of Allah) by it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2792
Abu al-Qasim Miqsam, the freed slave of Abdullah bin al-Harith bin Nawfal, said: A man from the people of Madinah narrated to me: I prayed in the mosque of Banu Ghifar. Then he mentioned his sitting, and said: I placed my left hand on my left thigh, placed my right hand on my right thigh, and raised my index finger upright. Khufaf bin Ima' bin Rahadah al-Ghifari (may Allah be pleased with him) saw me, and he was a Companion of the Messenger of Allah (peace and blessings be upon him). When I finished my prayer with the salam, he said to me: Why did you raise your finger upright like this? I said: I have seen people doing it like this. He said: You are right. Indeed, when the Messenger of Allah (peace and blessings be upon him) prayed, he would do this, and the polytheists would say that Muhammad (peace and blessings be upon him) does this with his finger in order to cast magic. They lied; the Messenger of Allah (peace and blessings be upon him) did this only to declare with it the Oneness of his Lord, the Blessed and Exalted.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2793
It is narrated from al-Ayzar (may Allah have mercy on him) that Ibn Abbas (may Allah be pleased with them both) was asked about a man who points with his finger while supplicating, and Ibn Abbas (may Allah be pleased with them both) said: Doing so is ikhlas (sincerity).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2794
(a) It is reported through another chain that Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: Doing so is ikhlas (sincerity).
(b) It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him): Doing so is humility.
(c) Uthman narrates from Mujahid (may Allah have mercy on him): It is a hammer against Satan.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2795
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "This is ikhlas (sincerity)," pointing with the finger next to his thumb; "and this is du'a (supplication)," and he raised his hands level with his shoulders; "and this is ibtihal (earnest imploring)," and he raised his hands high, stretched out.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2796