Islam requires funding Jihad through the tax of Zakat. Zakat is not charity as Muslims would have you believe. “Charity” for the poor specifically is Sedaqqa in Arabic. Zakat is prohibited from being given to non-believers – it is strictly reserved for Muslims. 2.5% of a muslim’s wealth, including Sharia-Compliant businesses are required to pay Zakat annually [Koran, 2:43, 2:195, 9:41] [Sahih Bukhari Hadith, Vol. 2, Book 24] [Reliance of the Traveller, h8.17, h9.0]
h8.17 The seventh category (Who can receive Zakat) is those fighting for Allah, meaning people engaged in Islamic military operations for whom no salary has been allotted in the army roster (O: but who are volunteers for jihad without remuneration). They are given enough to suffice them for the operation, even if affluent; of weapons, mounts, clothing, and expenses (O: for the duration of the journey, round trip, and the time they spend there, even if prolonged. Though nothing has been mentioned here of the expense involved in supporting such people’s families during this period, it seems clear that they should also be given it).
h8.24 It is not permissible to give zakat to a non-Muslim, or to someone whom one is obliged to support (def: m12.1), such as a wife or family member.
h1.2 Non-Muslims are not obliged to pay zakat, nor apostates from Islam (murtadd, def:o8) unless they return to Islam, in which case they must pay for the time they spent out of Islam, though if they die as non-Muslims their property is not subject to zakat(N:because their property is considered to belong to the Muslim common fund (bayt al-mal) from the moment such people leave Islam).