Qasim said: When a proposal was sent to Sayyidah Aishah (may Allah be pleased with her) for a woman of her family, she would act as a witness, and when it came to concluding the marriage contract, she would say to some of her family members: You conduct the marriage, for a woman cannot conclude a marriage contract.
Al-Shaykh (may Allah have mercy on him) said: This report indicates "There is no marriage without a guardian."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13652