Musannaf Ibn Abi Shayba 23:101

Abu Mu'awiyah narrated to us, from al-A'mash, from Dharr, from Wa'il ibn Muhana, who said: Abdullah said: "I have not seen anyone deficient in religion and opinion who is more overpowering to men of sound judgment regarding their affairs than women." They said: "O Abu Abd al-Rahman, and what is the deficiency of her religion?" He said: "Her leaving the prayer during the days of her menstruation." They said: "And what is the deficiency of her intellect?" He said: "The testimony of two women is not valid except as the testimony of one man."