(1) باب كَرَاهَةِ شِرَاءِ الإِنْسَانِ مَا تَصَدَّقَ بِهِ مِمَّنْ تَصَدَّقَ عَلَيْهِ
Ibn 'Umar reported that 'Umar b. al-Khattib (Allah be pleased with him) donated a horse in the path of Allah and (later on) he found it being sold, and he decided to buy that. He asked the Messenger of Allah (ﷺ) about it. whereupon he (the Holy prophet) said:
Don't buy that and do not get back what you gave in charity.
Reference: Sahih Muslim 1621 a
In-book reference: Book 24, Hadith 5
USC-MSA web (English) reference(deprecated numbering scheme): Book 12, Hadith 3952