Bukhari

Mujahid narrated that I expressed my intention to participate in jihad before Abdullah bin Umar (may Allah be pleased with them), so he said, "My heart desires that I also spend some of my wealth in this cause to help you." I said, "What Allah has given me is sufficient for me." But he said, "Your wealth is for you. I only wish that in this way my wealth may also be spent in the path of Allah." Umar (may Allah be pleased with him) said that many people take this wealth (from the treasury) on the condition that they will participate in jihad, but then they do not go for jihad. Therefore, whoever does this, we are more entitled to that wealth, and we will take back the wealth that he took (from the treasury). Tawus and Mujahid said that if something is given to you on the condition that you will go out for jihad in return, then you may spend it wherever you wish, and you may also use it for the needs of your family (but participation in jihad according to the condition is necessary).

Narrated `Umar bin Al-Khattab: I gave a horse to be used in Allah's Cause, but later on I saw it being sold. I asked the Prophet whether I could buy it. He said, "Don't buy it and don't take back your gift of charity."

(This above-mentioned chapter is not present in some copies, however, it is found in the edition researched by Shaykh Fuad Abdul Baqi.)