I saw the Messenger of Allah ﷺ placing his right hand on his right thigh during the prayer and pointing with his finger.
أخبرني محمد بن عبد الله بن عمار الموصلي عن المعافى عن عصام بن قدامة
رأيت رسول الله ﷺ واضعا يده اليمنى على فخذه اليمنى في الصلاة ويشير بأصبعه
[Its chain is hasan] Abu Dawud narrated it in the Book of Prayer, in the chapter on making a gesture during the tashahhud, hadith no. 991, from the hadith of Isam bin Qudama through this route. It is also found in al-Kubra, hadith no. 1194, and Ibn Khuzayma and Ibn Hibban graded it sahih.