Musnad Ahmad 30:2432

Yahya narrated to us, from Shu'bah, who said: 'Ata' ibn Abi Maymunah narrated to me, from Abu Rafi', from Abu Hurayrah, who said: "The name of Zaynab was Barrah, so the Prophet, peace and blessings of Allah be upon him, named her Zaynab."