Is it permissible for a soldier to donate the salary of the month he is on leave, with his consent, justifying his donation by saying that it will be stolen or become worthless if he does not donate it, with the aim of purchasing materials and equipment for the public funds of the state?

It is permissible for an individual to donate a portion of their wealth for the benefit of the Muslim state, as long as they are of sound mind and mature. This is an individual right affirmed by Islam for them, and they have the freedom to dispose of all or part of their wealth. Therefore, it is permissible to accept this donation and spend it on the general welfare of Muslims or as specified by the donor.