It is narrated from Sayyidah Aishah (may Allah be pleased with her) that he (peace and blessings be upon him) said: "Allah Almighty does not accept the prayer of a woman who has reached puberty without a head-covering." Sa'id bin Abi Arubah narrated this hadith from Qatadah, from al-Hasan (may Allah have mercy on him), from the Prophet (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3254