It is narrated from Hazrat Ubayy bin Ka'b (may Allah be pleased with him) that once I had a difference of opinion with Hazrat Umar (may Allah be pleased with him) regarding the ruling if a woman's husband passes away and she is pregnant. My opinion was that when she gives birth to the child, she can marry again. Upon this, my mother of the child, Umm Tufail, said to Hazrat Umar (may Allah be pleased with him) and me that the Prophet (peace and blessings of Allah be upon him) had instructed Sabi'ah Aslamiyyah that when she gives birth to the child, she can marry again.