Ali bin Abdul-Rahman reported,

Abdullah bin Umar saw me playing with pebbles during the prayer. When I finished, he forbade me from doing so and said, "Do as the Messenger of Allah ﷺ used to do."I asked, "How did the Messenger of Allah ﷺ do it?"He replied, "When he sat during the prayer, he would place his right palm on his right thigh, close all his fingers, and point with the finger next to the thumb. He would place his left palm on his left thigh. This is how the Messenger of Allah ﷺ used to do it."

عن علي بن عبد الرحمن المعاوي أنه قال

رآني عبد الله بن عمر، وأنا أعبث بالحصباء في الصلاة، فلما انصرفت نهائي وقال: اصنع كما كان رسول الله ﷺ يصنع، فقلت: وكيف كان رسول الله ﷺ يصنع؟ قال: كان إذا جلس في الصلاة وضع كفه اليمنى، وقبض أصابعه كلها، وأشار بإصبعه التي تلي الإبهام، ووضع كفه اليسرى على فخذه اليسرى، وقال: هكذا كان رسول الله ﷺ يفعل.