Sunan an-Nasa'i, Volume 3, Book 23, Hadith 2618 (DarusSalam) ⓘ

It was narrated from Salim bin 'Abdullah that 'Abdullah bin 'Umar used to narrate that: 'Umar give a house in charity for the sake of Allah, the Mighty and Sublime, and he found it being offered for sale after that. He wanted to buy it, then he went to the Messenger of Allah and asked him about that. The Messenger of Allah said: "Do not take back what you have given in charity."

أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ، قَالَ أَنْبَأَنَا حُجَيْنٌ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يُحَدِّثُ أَنَّ عُمَرَ، تَصَدَّقَ بِفَرَسٍ فِي سَبِيلِ اللَّهِ عَزَّ وَجَلَّ فَوَجَدَهَا تُبَاعُ بَعْدَ ذَلِكَ فَأَرَادَ أَنْ يَشْتَرِيَهُ ثُمَّ أَتَى رَسُولَ اللَّهِ صلى الله عليه وسلم فَاسْتَأْمَرَهُ فِي ذَلِكَ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ لاَ تَعُدْ فِي صَدَقَتِكَ ‏" ‏ ‏.‏