Musannaf Ibn Abi Shayba 20:31

Abu Bakr narrated to us, he said: Yahya bin Zakariya bin Abi Za'idah narrated to us, from al-Sha'bi, from Alqama, who said: A man came to Ibn Mas'ud and said: "A man among us married a woman, but he did not specify a dowry for her, nor did he have intercourse with her, until he died." Ibn Mas'ud said: "I have not been asked about anything since I parted from the Prophet, may Allah bless him and grant him peace, that was more difficult for me than this." He said: He hesitated regarding it for a month, then he said: "I will speak regarding it with my opinion. If it is correct, then it is from Allah, and if it is wrong, then it is from me and the Shaytan. I see that she has the dowry of the women of her status, neither less nor more, and she has the inheritance, and she must observe the waiting period ('iddah) of a woman whose husband has died." Then some people from Ashja' stood up and said: "We bear witness that the Messenger of Allah, may Allah bless him and grant him peace, judged with the same as what you have judged regarding a woman among us called Barwa' bint Washiq." He said: I have never seen Ibn Mas'ud as happy as he was on that day.