Sahih Muslim Book 009, Hadith Number 3537.
Chapter: The period of 'Idda comes to an end with the birth of the child.
Abu Salama b. 'Abd al-Rahman and Ibn 'Abbas.(Allah be pleased with them) got together in the house of Abu Huraira (Allah be pleased with him) and began to discuss about the woman who gave birth to a child a few nights after the death of her husband. Ibn 'Abbas (Allah be pleased with then)) said: Her 'Idda is that period which is longer of the two (between four months and ten days and the birth of the child, whichever is longer). AbuSalama, however said: Her period of 'Idda is over (with the birth of the child), and they were contending with each other over this issue, whereupon Abu Huraira (Allah be pleased with him) said: I subscribe (to the view) held by my nephew (i.e. Abu Salama). They sent Kuraib (the freed slave of Ibn 'Abbas) to Umm Salama to ask her about it. He came (back) to them and informed them that Umm Salama (Allah be pleased with her) said that Subai'ah al-Aslamiyya gave birth to a child after the death of her husband when the few flights (had hardly) passed and she made mention of that to Allah's Messenger (may peace be upon him) and he commanded her to marry.