Volume 4, Book 52, Number 247:
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 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.”