Musannaf Ibn Abi Shayba 9:1205

Ali ibn Mushir narrated to us, from Dawud, from al-Sha’bi, from Masruq and ‘Amr ibn ‘Utbah, that they wrote to Subay’ah bint al-Harith asking her about her affair. She wrote back to them that she had delivered [her child] twenty-five nights after the death of her husband. Then she adorned herself, seeking marriage. Abu al-Sanabil ibn Ba’kak passed by her and said, "You have been hasty. You must wait for the later of the two terms: four months and ten [days]." She said: So I came to the Prophet, peace and blessings of Allah be upon him, and said, "O Messenger of Allah, seek forgiveness for me." He said, "And what is that?" I informed him of the news. He said, "If you find a righteous husband, then marry."