‘Umar bin Al Khattab gave a horse as alms in the way of Allah. He then found it being sold, and intended to buy it. So he asked the Messenger of Allah ﷺ about this. He said Do not buy it, and do not take back your sadaqah.
أَنْ يَبْتَاعَهُ فَسَأَلَ رَسُولَ اللَّهِ ﷺ عَنْ ذَلِكَ فَقَالَ لاَ تَبْتَعْهُ وَلاَ تَعُدْ فِي صَدَقَتِكَ