Sunan an-Nasa’i 3509
The Book of Divorce
The 'Iddah Of A Pregnant Woman Whose Husband Dies
Abu Salamah said: "Abu Hurairah and Ibn 'Abbas differed concerning the widow who gives birth after her husband's death. Abu Hurairah said: 'She may be married.' Ibn 'Abbas said: '(She has to wait) for the longer of the two periods.' They sent word to Umm Salamah and she said: 'The husband of Subai'ah died and she gave birth fifteen days -half a month- after her husband died.' She said: 'Two men proposed marriage to her, and she was inclined toward one of them. When they feared that she was becoming single-minded (on this issue, and not consulting her family), they said: It is not permissible for you to marry. She went to the Messenger of Allah and he said: 'It is permissible for you to marry, so marry whomever you want.''"