From Sahih Muslim (Hadith 5761):
A'isha reported:we (intended to pour) medicine in the mouth of Allah's Messenger (ﷺ) in his illness, but he pointed out (with the gesture of his hand) that it should not be poured into the mouth against his will. We said: (It was perhaps due to the natural) aversion of the patient against medicine. When he recovered, he said: Medicine should be poured into the mouth of every one of you except Ibn 'Abbas, for he was not present amongst you
Reference: Muslim 5761