`Umar gave a horse to be used in Allah's Cause, but later on he found it being sold. So, he intended to buy it and asked Allah's Messenger (ﷺ) who said, "Don't buy it and don't take back your gift of charity."
Sahih al-Bukhari Book 56, Hadith 180
← Previous Hadith I gave a horse to be used in Allah's Cause, but later on I saw it being sold. I asked the Prophet (ﷺ) whether I could buy it. He said, "Don't buy it and don't take back your gift of charity."

Sahih al-Bukhari Book 56, Hadith 179 Next Hadith → Allah's Messenger (ﷺ) said, "Were it not for the fear that it would be difficult for my followers, I would not have remained behind any Sariya, (army-unit) but I don't have riding camels and have no other means of conveyance to carry them on, and it is hard for me that my companions should remain behind me. No doubt I wish I could fight in Allah's Cause and be martyred and come to life again to be martyred and come to life once more."

Sahih al-Bukhari Book 56, Hadith 181