Genesis 17:10

10.Every man-child among you shall be circumcised Although God promised alike to males and females, what he afterwards sanctioned by circumcision, he nevertheless consecrated, in one sex, the whole people to himself. For whereas, by this symbol, the promise which was given, indiscriminately, to males and females, is confirmed, and it is certain that females as well as males had need of confirmation, it is hence evident, that the symbol was ordained for the sake of both sexes. Nor is it of any force in opposition to this reasoning to say that each individual is commanded to communicate in the sacraments, if he would derive any benefit from them, on the ground that no profit is received by those who neglect their use. For the covenant of God was graven on the bodies of the males, with this condition annexed, that the females also should as their associates be partakers of the same sign.