"The Messenger of Allah said: 'The likeness of the one who takes back his gift, is that of a dog which goes back to its vomit and eats it.'"  

قَالَ رَسُولُ اللَّهِ ﷺ مَثَلُ الَّذِي يَرْجِعُ فِي صَدَقَتِهِ كَمَثَلِ الْكَلْبِ يَرْجِعُ فِي قَيْئِهِ فَيَأْكُلُهُ  

Once I gave a horse in Allah's Cause (in charity) but that person did not take care of it. I intended to buy it, as I thought he would sell it at a low price. So, I asked the Prophet ﷺ about it. He said, "Neither buy, nor take back your alms which you have given, even if the seller were willing to sell it for one Dirham, for he who takes back his alms is like the one who swallows his own vomit."  

سَمِعْتُ عُمَرَ ؓ يَقُولُ حَمَلْتُ عَلَى فَرَسٍ فِي سَبِيلِ اللَّهِ فَأَضَاعَهُ الَّذِي كَانَ عِنْدَهُ فَأَرَدْتُ أَنْ أَشْتَرِيَهُ وَظَنَنْتُ أَنَّهُ يَبِيعُهُ بِرُخْصٍ فَسَأَلْتُ النَّبِيَّ ﷺ فَقَالَ لاَ تَشْتَرِ وَلاَ تَعُدْ فِي صَدَقَتِكَ وَإِنْ أَعْطَاكَهُ بِدِرْهَمٍ فَإِنَّ الْعَائِدَ فِي صَدَقَتِهِ كَالْعَائِدِ فِي قَيْئِهِ  

I heard ʿUmar bin Al-Khattab saying, "I gave a horse to be ridden in Allah's Cause and the person who got it intended to sell it or neglected it. So, I wanted to buy it as I thought he would sell it cheap. I consulted the Prophet ﷺ who said, "Do not buy it even if for one Dirham, because he who takes back his gift is like a dog swallowing its vomit."  

أَنَّهُ بَائِعُهُ بِرُخْصٍ فَسَأَلْتُ النَّبِيَّ ﷺ فَقَالَ لاَ تَشْتَرِهِ وَإِنْ بِدِرْهَمٍ فَإِنَّ الْعَائِدَ فِي هِبَتِهِ كَالْكَلْبِ يَعُودُ فِي قَيْئِهِ