It is narrated from Abu al-Sanabil bin Ba'kak (may Allah be pleased with him); he said: Sayyidah Subay'ah (may Allah be pleased with her) gave birth twenty-three nights after the death of her husband, and then she desired to marry. The matter was brought to the Prophet (peace and blessings be upon him) and he was informed, and he (peace and blessings be upon him) said: "If she wishes to do so, her waiting period ('iddah) has been completed."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14151