I asked Abu Abdullah Imam Jafar ibn Muhammad Al-Sadiq (as) about why women were exempted from jizya and it was not imposed on them. He said: "Because the Messenger of Allah (swt), peace be upon him and his family, forbade the killing of women and children in the battlefield (Dar al-Harb), unless they engage in fighting. Even if a woman fights, avoid harming her as much as possible unless there is a fear of harm or disruption. Since the Messenger of Allah (swt), peace be upon him and his family, prohibited their killing in Dar al-Harb, their exemption in Dar al-Islam is even more appropriate. If a woman refuses to pay the jizya, it is not permissible to kill her. Therefore, since it is not permissible to kill her, the jizya was lifted from her. However, if men refuse and abstain from paying the jizya, they breach the covenant (dhimma), making their blood permissible and their killing lawful. This is because killing men is allowed in Dar al-Shirk and under the covenant if they violate its terms. Similarly, the paralyzed among the polytheists and people under covenant (dhimma), the blind, the very old, women, and children in the battlefield (Dar al-Harb) are also exempted from jizya because of this reasoning."