Musnad Abu Ya'la al-Mawsili 110:225

Muhammad said: Someone whom I do not accuse narrated that to me, from Yazid ibn Hurmuz, that he was in his writing asking him about the slaves: Did they attend war with the Messenger of Allah, may Allah bless him and grant him peace? And was a share struck for them? And about the orphan: When does he exit from orphanhood and his right in the *fay* (spoils) fall due? So he wrote to him that the slaves did indeed attend war with the Messenger of Allah, may Allah bless him and grant him peace. As for a share being struck for them, then no, but he used to give them a gift (*radkh*). And as for the orphan, when he reaches puberty, he exits from orphanhood and his right in the *fay* falls due.