(137) باب إِذَا حَمَلَ عَلَى فَرَسٍ فَرَآهَا تُبَاعُ
Narrated Aslam:
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."
Reference: Sahih al-Bukhari 3003
In-book reference: Book 56, Hadith 212
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 52, Hadith 247