Musannaf Ibn Abi Shayba 9:1206

Shababa narrated to us, from Shu'bah, from Ubayd ibn al-Hasan, from Abd al-Rahman ibn Mughaffal, who said: I witnessed Ali, and a man asked him about a woman whose husband died while she was pregnant. He said: "She shall wait for the furthest of the two terms." Ibn Mas'ud said: "We say she may marry herself off." Ali said: "Indeed, Farrukh does not know."