مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2849
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) took one-fifth (khumus) of buried treasure.
Musnad Ahmad 2869Saheeh because of corroborating evidence]