Sahih al-Bukhari 3003
Sahih al-Bukhari · Book 56: Fighting for the Cause of Allah (Jihaad) · If someone gives his horse for Allah's Cause and then he sees it being sold
Narrated Aslam:
حَدَّثَنَا إِسْمَاعِيلُ ، حَدَّثَنِي مَالِكٌ ، عَنْ زَيْدِ بْنِ أَسْلَمَ ، عَنْ أَبِيهِ ، قَالَ سَمِعْتُ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ يَقُولُ حَمَلْتُ عَلَى فَرَسٍ فِي سَبِيلِ اللَّهِ فَابْتَاعَهُ ـ أَوْ فَأَضَاعَهُ ـ الَّذِي كَانَ عِنْدَهُ، فَأَرَدْتُ أَنْ أَشْتَرِيَهُ، وَظَنَنْتُ أَنَّهُ بَائِعُهُ بِرُخْصٍ، فَسَأَلْتُ النَّبِيَّ صلى الله عليه وسلم فَقَالَ " لاَ تَشْتَرِهِ وَإِنْ بِدِرْهَمٍ، فَإِنَّ الْعَائِدَ فِي هِبَتِهِ كَالْكَلْبِ يَعُودُ فِي قَيْئِهِ " .
I heard `Umar 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."