سنن النسائي

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 (ﷺ) and he told her to get married."