Volume 2, Book 24, Number 567:
Narrated ‘Umar:
Once I gave a horse in Allah’s Cause (in charity) but that person did not take care of it. I intended
to buy it, as I thought he would sell it at a low price. So, I asked the Prophet (p.b.u.h) about it. He said,
“Neither buy, nor take back your alms which you have given, even if the seller were willing to sell it
for one Dirham, for he who takes back his alms is like the one who swallows his own vomit.”