Not to take back presents or Sadaqa

Narrated 'Umar bin Al-Khattab:

I gave a horse in Allah's Cause. The person to whom it was given, did not look after it. I intended to buy it from him, thinking that he would sell it cheap. When I asked the Prophet he said, "Don't buy it, even if he gives it to you for one Dirham, as the person who takes back what he has given in charity, is like a dog that swallows back its vomit."

حَدَّثَنَا إِبْرَاهِيمُ بْنُ مُوسَى، أَخْبَرَنَا هِشَامُ بْنُ يُوسُفَ، أَنَّ ابْنَ جُرَيْجٍ، أَخْبَرَهُمْ قَالَ أَخْبَرَنِي عَبْدُ اللَّهِ بْنُ عُبَيْدِ اللَّهِ بْنِ أَبِي مُلَيْكَةَ، أَنَّ بَنِي صُهَيْبٍ، مَوْلَى ابْنِ جُدْعَانَ ادَّعَوْا بَيْتَيْنِ وَحُجْرَةً، أَنَّ رَسُولَ اللَّهِ ﷺ أَعْطَى ذَلِكَ صُهَيْبًا، فَقَالَ مَرْوَانُ مَنْ يَشْهَدُ لَكُمَا عَلَى ذَلِكَ قَالُوا ابْنُ عُمَرَ. فَدَعَاهُ فَشَهِدَ لأَعْطَى رَسُولُ اللَّهِ ﷺ صُهَيْبًا بَيْتَيْنِ وَحُجْرَةً. فَقَضَى مَرْوَانُ بِشَهَادَتِهِ لَهُمْ.