"...If the party liable is mentally deficient, or weak, or unable Himself to dictate, Let his guardian dictate faithfully, and get two witnesses, out of your own men, and if there are not two men, then a man and two women, such as ye choose, for witnesses, so that if one of them errs, the other can remind her. The witnesses should not refuse when they are called on (For evidence)." - Quran 2:282 (read more)

"....The women asked, "O Allah's Apostle! What is deficient in our intelligence and religion?" He said, "Is not the evidence of two women equal to the witness of one man?" They replied in the affirmative. He said, "This is the deficiency in her intelligence. Isn't it true that a woman can neither pray nor fast during her menses?" The women replied in the affirmative. He said, "This is the deficiency in her religion." - Sahih Bukhari 1:6:301 (read more)

"And [as for] those of your women who (read allā'ī or allā'i in both instances) no longer expect to menstruate, if you have any doubts, about their waiting period, their prescribed [waiting] period shall be three months, and [also for] those who have not yet menstruated, because of their young age, their period shall [also] be three months - both cases apply to other than those whose spouses have died; for these [latter] their period is prescribed in the verse: they shall wait by themselves for four months and ten [days] [Q. 2:234]." - al-Jalalayn