It was narrated that Tawus said: "The Messenger of Allah (ﷺ) said: 'It is not permissible for anyone to give a gift then take it back, except from one's son.'" Tawus said: "When I was young I used to hear (the phrase), 'The one who goes back to his vomit,' but we did not realize that this was a similitude." He said: "The likeness of the one who does that is that of a dog which eats then vomits, then goes back to its vomit."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا مُحَمَّدُ بْنُ حَاتِمٍ، قَالَ حَدَّثَنَا حِبَّانُ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ إِبْرَاهِيمَ بْنِ نَافِعٍ، عَنِ الْحَسَنِ بْنِ مُسْلِمٍ، عَنْ طَاوُسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ يَحِلُّ لأَحَدٍ أَنْ يَهَبَ هِبَةً ثُمَّ يَرْجِعَ فِيهَا إِلاَّ مِنْ وَلَدِهِ " . قَالَ طَاوُسٌ كُنْتُ أَسْمَعُ وَأَنَا صَغِيرٌ عَائِدٌ فِي قَيْئِهِ فَلَمْ نَدْرِ أَنَّهُ ضَرَبَ لَهُ مَثَلاً قَالَ " فَمَنْ فَعَلَ ذَلِكَ فَمَثَلُهُ كَمَثَلِ الْكَلْبِ يَأْكُلُ ثُمَّ يَقِيءُ ثُمَّ يَعُودُ فِي قَيْئِهِ " .
sunnah.com