I heard Ibn al-Zubair say: Setting the feet right and placing one hand on the other is a sunnah.
Sunan Abi Dawud Book 2, Hadith 364
← Previous Hadith When the Messenger of Allah (ﷺ) began his prayer, he raised his hands extensively.

Sunan Abi Dawud Book 2, Hadith 363 Next Hadith → AbuUthman an-Nahdi said: When Ibn Mas'ud prayed he placed his left hand on the right. The Prophet (ﷺ) saw him and placed his right hand on his left one.

Sunan Abi Dawud Book 2, Hadith 365