Sayyiduna Abu al-Sanabil bin Ba'kak (may Allah be pleased with him) said: Sayyidah Subay'ah (may Allah be pleased with her) gave birth twenty-three or twenty-five days after the death of her husband. When she became pure from her postnatal bleeding, she showed a desire (for marriage), and this was mentioned to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "If she does so, her waiting period has been completed."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 19100