مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2115
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas (رضي الله عنه), from the Prophet (ﷺ), that He said regarding the skins of dead animals: "Tanning takes away their badness, filth or impurity.”
Musnad Ahmad 2117Hasan]