مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2872
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) said: I was commanded to use the siwak until I feared that revelation would be sent to me concerning it.
Musnad Ahmad 2893Hasan because of corroborating evidence; this is a da'eef is