Umar bin Khattab reported,

I gave a noble horse as a contribution in the cause of Allah, and the man who had it had neglected it. I wanted to buy it back from him, thinking he would sell it cheaply. So I asked the Messenger of Allah ﷺ about that.He said, "Do not buy it back, even if he gives it to you for a single dirham, for the one who takes back his charity is like the dog that returns to its vomit."

Azami 4138

Sahih

عن عمر بن الخطاب، قال

حملت على فرس عتيق في سبيل الله وكان الرجل الذي هو عنده قد أضاعه فأردت أن أشتريه منه وظننت أنه بائعه برخص فسألت عن ذلك رسول الله ﷺ فقال: لا تشتره وإن أعطاكه بدرهم واحد؛ فإن العائد في صدقيه كالكلب يعود في قينه.

الأعظمي 4138صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Zakat
Chapter
Encouragement to pay zakat and charity and the ways of spending them
Section
Dislike of purchasing what one has given in charity
Numbering
Jami al-Kamil 4138 (2nd edition)
Azami 4138