(196) بَابُ مَنْ كَرِهَ أَمْثَالَ السَّوْءِ
Ibn 'Abbas reported that the Prophet, may Allah bless him and granthim peace, said, "We do not give a bad example. The one who takes backhis gift is like the dog who returns to his own vomit."
Reference: Al-Adab Al-Mufrad 417
In-book reference: Book 23, Hadith 3
English translation: Book 23, Hadith 417