Narrated by:`Abdullah bin `Umar
Narrated `Abdullah bin `Umar:`Umar bin Al-Khattab gave a horse to be ridden in Allah's Cause and then he found it being sold. He intended to purchase it. So, he consulted Allah's Messenger (ﷺ) who said, "Don't buy it and don't take back your gift of charity."
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنْ نَافِعٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ ـ رضى الله عنهما أَنَّ عُمَرَ بْنَ الْخَطَّابِ، حَمَلَ عَلَى فَرَسٍ فِي سَبِيلِ اللَّهِ فَوَجَدَهُ يُبَاعُ، فَأَرَادَ أَنْ يَبْتَاعَهُ، فَسَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم فَقَالَ " لاَ تَبْتَعْهُ، وَلاَ تَعُدْ فِي صَدَقَتِكَ ".
Bukhari
Fighting for the Cause of Allah (Jihaad) • Hadith 211