Musannaf Ibn Abi Shayba 9:845

Ibn ‘Ulayyah narrated to us, from Ibn Abi Najih, from Mujahid, who said: He shall not marry [her] until the waiting period of the woman he divorced has ended. And ‘Ata’ said: If there is no inheritance between them and he does not have the right of return over her, then there is no harm in him marrying [her].