Volume 2, Book 24, Number 566:
Narrated ‘Abdullah bin ‘Umar:
Umar bin Al-Khattab gave a horse in charity in Allah’s Cause and later he saw it being sold in the
market and intended to purchase it. Then he went to the Prophet and asked his permission. The
Prophet said, “Do not take back what you have given in charity.” For this reason, Ibn ‘Umar never
purchased the things which he had given in charity, and in case he had purchased something (un –
knowingly) he would give it in charity again.
Volume 2 – 343 / 1700
SAHIH BUKHARI VOLUME 2 > BOOK 24: OBLIGATORY CHARITY TAX (ZAKAT)