(a) It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that when the Messenger of Allah (peace and blessings be upon him) sat for the tashahhud, he would place his right palm on his right thigh and his left palm on his left thigh, and form the knot of fifty-three and supplicate.
(b) Imam Muslim (may Allah have mercy on him) recorded this narration in his Sahih with his own chain, but in it the wording is that he formed the knot of fifty-three (53) and pointed with the index finger.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2781