مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3174
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn 'Abbas (رضي الله عنه) said: I heard the Messenger of Allah (ﷺ) say: “Any (animal) skin has been tanned has become pure.
Musnad Ahmad 3198Its isnad is saheeh, Muslim (366)]