Musnad Ahmad 1156:186

Muhammad ibn Ja'far and Hajjaj narrated to us, they said: Shu'bah narrated to us, he said: I heard 'Abd Rabb ibn Sa'id—Hajjaj said: And 'Abd Rabbih ibn Sa'id, the brother of Yahya ibn Sa'id—he said: I heard Abu Salamah ibn 'Abd al-Rahman, he said: Abu Hurayrah and Ibn 'Abbas differed regarding the woman whose husband has died, if she delivers her pregnancy. Abu Hurayrah said: "She may marry." And Ibn 'Abbas said: "The longer of the two terms." He said: So they sent to Umm Salamah, and she said: The husband of Subay'ah bint al-Harith died, and she gave birth fifteen nights after his death. She said: Two men proposed to her. She said: So she inclined toward one of them. When they feared that she might act on her own behalf toward one of them, they said: "You have not become lawful [to marry]." So she went to the Messenger of Allah, peace and blessings of Allah be upon him, and he said: "You have become lawful, so marry whom you wish."