Ibn ‘Abbas reported God’s Messenger as saying, "One who seeks to take back a gift is like a dog which returns to its vomit. An evil example does not apply to us*.” * i.e. to Muslims. Bukhari transmitted it.

وَعَنِ ابْنِ عَبَّاسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الْعَائِدُ فِي هِبَتِهِ كَالْكَلْبِ يَعُودُ فِي قَيْئِهِ لَيْسَ لَنَا مَثَلُ السوء» . رَوَاهُ البُخَارِيّ