Ibn 'Abbas reported that the Prophet, may Allah bless him and grant him peace, said, "We do not give a bad example. The one who takes back his gift is like the dog who returns to his own vomit."  

عَنِ النَّبِيِّ ﷺ قَالَ لَيْسَ لَنَا مَثَلُ السَّوْءِ الْعَائِدُ فِي هِبَتِهِ كَالْكَلْبِ يَرْجِعُ فِي قَيْئِهِ