Musannaf Ibn Abi Shayba 13:1543

Abu Bakr narrated to us, he said: Ubaydullah narrated to us, from Uthman ibn al-Aswad, from Ata and Mujahid, they both said: "For the orphan girl, there are two restrictions: nothing of her wealth is permissible for her until she gives birth to a child or a year passes for her in the house of her husband."