Sunan An-Nasa'i

It was narrated from Sulaiman bin Yasir that Abu Hurairah, Ibn 'Abbas, and Abu Salamah bin 'Abdur-Rahman were talking about the 'Iddah of a woman whose husband dies, and she gives birth after her husband dies. Ibn 'Abbas said:""She should observe 'Iddah for the longer of the two periods."" Abu Salamah said: ""No, it becomes permissible for her to marry when she has given birth."" Abu Hurairah said: ""I agree with my brother's son."" So they sent word to Umm Salamah, the wife of the Prophet, and she said: ""Subai'ah Al-Aslamiyyah gave birth shortly after her husband died; she consulted the Messenger of Allah and he told her to get married