It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said that Sayyidah Subay'ah (may Allah be pleased with her) gave birth after the death of her husband, and two men proposed marriage to her. People said: She has not yet become lawful (for marriage). So I mentioned this to the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) said: "You have become lawful, so marry whomever you wish."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19850