Surah Al-Baqarah...
And Allah straitens and extends and unto Him you will be returned." From here on the verses of Holy War come forth. It begins with the command of fighting in the path of Allah, and warns us to beware that He hears what we say and knows what we have in our hearts, from our motives and intentions, regarding the Holy War in the way of Allah.
It says: "And fight in the way of Allah, and know that Allah is All-Hearing, All-Knowing." In spite of all that has been said that Islam prefers peaceful methods of preaching the truth, and that it never took any initiative in waging war against its opponents, the fact is that Islam recognizes the right of taking even the initiative in using force against those who persist in ungodly activities causing human degradation or social or moral deterioration.
But this measure cannot be adopted save by the Prophet of Allah or his Vicegerent authorized by him and none else. As the fifth Holy Imam Muhammad Ibne-Ali Al-Baqir (as) says **'** A war may be termed as holy or godly (jihad)' if the object be to make people give up submission to anyone besides Allah, and to submit only to God's authority and the Divine Will.
But if the object be to make them give up submission to one creature in order to submit to any other, it is the usual war waged for selfish and some worldly gain. Hence it is unholy and thus condemned by Islam.
However, Islam enjoins on Muslims to be always ready, well prepared and well equipped to meet all exigencies or an eventuality which may unexpectedly develop against them, and then they should gather strength as much as they can so that their opponents, the opponents of the divine cause may refrain from any unprovoked aggression. Occasion Of Revelation It is narrated that the holy Prophet (S) once said that whoever gives any alms will receive it twice in Heaven.
Abud-Dahdah Ansari, addressing the Messenger of Allah (S) , said that he had two gardens and questioned if he donated one of them as alms, would he have it twice in Heaven? Then the Prophet replied him positively.