مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3095
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Moosa bin Salamah said: I asked Ibn ‘Abbas (رضي الله عنه): How should I pray when I am in Makkah if I do not pray with the imam? He said: Two rak’ahs, the Sunnah of Abul-Qasim (ﷺ).
Musnad Ahmad 3119its isnad is saheeh, Muslim (688)]