Abu Dawud
Commercial Transactions
Book Number: 016 / Hadith Number: 3351
Narated By Abdullah ibn Amr ibn al-'As : The Apostle of Allah (pbuh) commanded him to equip an army, but the camels were insufficient. So he commanded him to keep back the young camels of sadaqah, and he was taking a camel to be replaced by two when the camels of sadaqah came.