he gave someone a horse to ride in the cause of Allah, then he saw it offered for sale and wanted to buy it. The Prophet said to him: "Do not think of buying back what you have given in charity." (Using translation from Nasāʾī 2616)
أَنَّهُ حَمَلَ عَلَى فَرَسٍ فِي سَبِيلِ اللهِ فَرَآهَا تُبَاعُ فَأَرَادَ شِرَاءَهَا فَقَالَ لَهُ النَّبِيُّ ﷺ «لَا تَعْرِضْ فِي صَدَقَتِكَ»