Musnad Abu Ya'la al-Mawsili 110:78

Narrated to us Zuhayr, narrated to us Ibn ‘Uyaynah, from Ayyub, from ‘Ikrimah, from Ibn ‘Abbas, from the Prophet (may Allah bless him and grant him peace), who said: "It is not for us to have a bad example: the one who takes back his gift is like the dog that returns to its vomit."