Sunan Abu Dawud
732
Sahih+3

The above mentioned tradition has also been reported by Muhammad b. ‘Amr b. ‘Ata’ through a different chain of narrators. This version adds:“When he prostrated himself he neither placed his arms on the ground nor closed them; putting forward his fingers towards the qiblah.”

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid