مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3102
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn Sireen that A funeral passed by al-Hasan and Ibn Abtas; al-Hasan stood up and Ibn 'Abbas did not. Al-Hasan said to Ibn 'Abbas: Didn't the Messenger of Allah stand up (for funerals)? He said: He stood up (sometimes) and he remained seated (sometimes).
Musnad Ahmad 3126Hasan because of corroborating evidence, and its isnad is da