Once I gave a horse (for riding) in Allah's Cause. Later I saw it being sold. I asked Messenger of Allah ﷺ (whether I could buy it). He said, "Don't buy it, for you should not get back what you have given in charity."  

عُمَرُ ؓ حَمَلْتُ عَلَى فَرَسٍ فِي سَبِيلِ اللَّهِ فَرَأَيْتُهُ يُبَاعُ فَسَأَلْتُ رَسُولَ اللَّهِ ﷺ فَقَالَ لاَ تَشْتَرِ وَلاَ تَعُدْ فِي صَدَقَتِكَ  

Once ʿUmar gave a horse in charity to be used in holy fighting. It had been given to him by Allah's Apostle . ʿUmar gave it to another man to ride. Then ʿUmar was informed that the man put the horse for sale, so he asked Messenger of Allah ﷺ whether he could buy it. Messenger of Allah ﷺ replied, "You should not buy it, for you should not take back what you have given in charity."  

أَنَّ عُمَرَ حَمَلَ عَلَى فَرَسٍ لَهُ فِي سَبِيلِ اللَّهِ أَعْطَاهَا رَسُولَ اللَّهِ ﷺ لِيَحْمِلَ عَلَيْهَا رَجُلاً فَأُخْبِرَ عُمَرُ أَنَّهُ قَدْ وَقَفَهَا يَبِيعُهَا فَسَأَلَ رَسُولَ اللَّهِ ﷺ أَنْ يَبْتَاعَهَا فَقَالَ لاَ تَبْتَعْهَا وَلاَ تَرْجِعَنَّ فِي صَدَقَتِكَ  

[Machine] "That Umar was riding a horse and Umar ibn Al-Khattab, the messenger of Allah, gave it to him so that a man could ride on it. Umar was then informed that he had stopped selling her. He asked the Prophet about this and the Prophet said, 'Do not buy her and do not count it as charity.'"  

أَنَّ عُمَرَ حَمَلَ عَلَى فَرَسٍ فَأَعْطَاهَا عُمَرُ رَسُولَ اللهِ ﷺ لِيَحْمِلَ عَلَيْهَا رَجُلًا فَأُخْبِرَ عُمَرُ أَنَّهُقَدْ وَقَفَهَا يَبِيعُهَا قَالَ فَسَأَلَ عَنْ ذَلِكَ النَّبِيَّ ﷺ يَبْتَاعُهَا قَالَ لَا تَبْتَعْهَا وَلَا تَعُدْ فِي صَدَقَتِكَ