مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2509
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: I saw the Messenger of Allah (ﷺ) prostrate during (Soorat) Sad.
Musnad Ahmad 2521Its isnad is saheeh, al-Bukhari (1069)]