Hadith 9:31
Yazid ibn Harun narrated to us, from Yazid, who said: I heard al-Hasan saying: There is no marriage except with a guardian, and two just witnesses, and a known dowry, and it being witnessed publicly.
حدثنا يزيد بن هارون عن يزيد قال سمعت الحسن يقول لا نكاح إلا بولي وشاهدي عدل وبصدقة معلومة ومشهود علانية