مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2544
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: The Prophet (ﷺ) put Zuhr and ‘Asr together in Madinah, when he was not travelling and there was no fear. I (the narrator) said: O Abul-'Abbas, why did he do that? He said: He did not want to make things difficult for anyone of his ummah.
Musnad Ahmad 2557Its isnad is saheeh, Muslim (705)]