مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3516
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas (رضي الله عنه) that The Messenger of Allah (ﷺ) rinsed his mouth after drinking milk and said: "It is somewhat greasy.”
Musnad Ahmad 3538lts isnad is saheeh, al-Bukhari (211) and Muslim (358)]