مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3241
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: I prayed with the Prophet (ﷺ) eight (rak'ahs) together and seven together. I (the narrator) said to Ibn 'Abbas: Why did he do that? He said: He wanted not make things difficult for his ummah.
Musnad Ahmad 3265Its isnad is saheeh, Muslim (705)]