Musnad Ahmad 8:5

Abu Amir narrated to us, Abdullah bin Ja'far narrated to us, from Ismail bin Muhammad bin Sa'd, from Amir bin Sa'd, that Sa'd rode to his palace in Al-Aqiq and found a young boy beating trees—or cutting them—so he took his belongings (as spoils). When Sa'd returned, the family of the young boy came to him and spoke to him to return what he had taken from their boy. He said: "I seek refuge in Allah from returning something that the Messenger of Allah (peace and blessings of Allah be upon him) granted to me as spoils," and he refused to return them to them.