Sahih al-Bukhari 5319
Sahih al-Bukhari · Book 68: Divorce · "For those who are pregnant, their 'Idda is until they laydown their burdens."
Narrated `Abdullah bin `Abdullah:
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ ، عَنِ اللَّيْثِ ، عَنْ يَزِيدَ ، أَنَّ ابْنَ شِهَابٍ ، كَتَبَ إِلَيْهِ أَنَّ عُبَيْدَ اللَّهِ بْنَ عَبْدِ اللَّهِ ، أَخْبَرَهُ عَنْ أَبِيهِ ، أَنَّهُ كَتَبَ إِلَى ابْنِ الأَرْقَمِ أَنْ يَسْأَلَ، سُبَيْعَةَ الأَسْلَمِيَّةَ كَيْفَ أَفْتَاهَا النَّبِيُّ صلى الله عليه وسلم فَقَالَتْ أَفْتَانِي إِذَا وَضَعْتُ أَنْ أَنْكِحَ.
that his father had written to Ibn Al-Arqam a letter asking him to ask Subai'a Al-Aslamiya how the Prophet had given her the verdict. She said, "The Prophet, gave me his verdict that after I gave birth, I could marry."