Musannaf Ibn Abi Shayba 10:1384

Abu Bakr narrated to us, he said: Zayd ibn al-Hubab narrated to us, from Ibn Lahi'ah, from Ubayd Allah ibn Abi Ja'far, from Bukayr ibn Abd Allah ibn al-Ashajj, from Sa'id ibn al-Musayyib, regarding a man who said to his wife, "You are divorced," and did not specify the number of divorces. He said: We make him swear to that, whether he intended one, or two, or three.