Amr bin Harish (may Allah have mercy on him) narrates: I said to Sayyiduna Abdullah bin Amr (may Allah be pleased with them both): We live in a land where there is neither gold nor silver; may we sell one camel for two camels, one cow for two cows and one goat for two goats? He said: The Messenger of Allah (peace and blessings be upon him) commanded me to equip an army, and the camels ran out. I said: O Messenger of Allah, the camels have run out. He (peace and blessings be upon him) said: "Take young she-camels of the charity (sadaqah) for me." So I began taking one camel in exchange for two camels from the charity camels.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13752