Musannaf Ibn Abi Shayba 5:851

'Abd al-Rahim narrated to us, from 'Amr ibn Maymun ibn Mihran, from Ziyad ibn Abi Maryam, from his mother, who said: I came to 'Abd Allah ibn al-Arqam—and he was in charge of the public treasury (Bayt al-Mal) during the affair of 'Uthman—while he was distributing charity in Medina. When he saw me, he said, "What brought you, O Umm Ziyad?" I said, "What brought the people to you." He said, "Have you been emancipated yet?" I said, "No." So he sent to his house and a garment (burd) was brought, and he ordered it for me, and he did not order anything for me from the charity because I was a slave.