Sayyidah Aishah (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) said: "Marriage is only in the presence of a guardian and two upright witnesses." Imam al-Shafi'i (may Allah have mercy on him) says: It is narrated from al-Hasan bin Abi al-Hasan that the Messenger of Allah (peace and blessings be upon him) said: "Marriage is in the presence of a guardian and two upright witnesses."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13719