Sayyiduna Saeed bin Zaid bin Amr bin Nufail (may Allah be pleased with him) narrates this statement of the Noble Prophet (peace and blessings of Allah be upon him): "Whoever is killed while protecting his wealth is a martyr, and whoever unlawfully acquires even a span of another's land, he will be made to wear a collar as heavy as seven earths." (Imam Ibn Hibban, may Allah have mercy on him, says:) The Noble Prophet (peace and blessings of Allah be upon him) has affirmed martyrdom for the one who is killed while protecting his wealth, and has permitted him to fight his killer. The narration is general, so when it becomes permissible for a person to fight a Muslim whose blood is inviolable in order to protect his wealth, then it will be even more permissible for a person to fight someone whose blood or wealth is not inviolable for him, whether that person is a child, an adult woman, or a slave, so it is more likely that such an action is permissible.