Said Ash-Shaykh Sâlih Al-Fauzân may Allâh preserve him in Al-Mul'khas Al-Fiq'hee
Allâh legislated Jihâd in His path to exalt His Word, help His Deen and bring down His enemies; He also made it a law so as to serve as a test and trial for His slaves:
but if it had been Allâh's will, He himself could certainly have punished them (without you). But (He lets you fight), in order to test you, some with others. But those who are killed in the way of Allâh, He will never let their deeds be lost. He will guide them and set right their state. [Muhammad: 4-5].
Jihâd in the path of Allâh has a great importance; it is the peak of the Islamic matters and one of the best acts of worship. Some scholars classify it as the sixth pillar of Islam.
Jihâd in the path of Allâh is a legislation derived from the Qur'ân, Sunnah and Ij'mâ (the Consensus of the Companions). Allâh the Majestic said:
Jihâd (fighting in Allâh's Cause) is ordained for you (Muslims)
So also is the act of the Prophet SallaLlâhu alahy wa sallam and of course, his command by mouth. He SallaLlâhu alahy wa sallam said:
'Whoever dies and did not fight (in Jihâd), and did not communicate with his heart that he would fight, he dies on a branch of nifâq.' [Muslim].
Jihâd is the root word of Jâhada which means 'he strove hard in fighting his enemy.' According to the Shariah, it is fighting the enemy. Jihâd yet has a more general meaning than fighting.
Ibn Qayyim may Allâh bestow His mercy on him said: 'Jihâd is an individual obligation; whether with the heart, with the tongue or with the hand. It is imperative on all Muslims to make striving with one of these types of Jihâd.' End of quote (from the statement of Ibn Qayyim may Allâh bestow mercy on him).
Jihâd is also connotatively used to refer to striving against the self, devil or the sinners. Striving against the self comes in from of learning the matters of the Deen, acting with them and teaching them to others.
As for striving against the devil, it is in terms of blocking the doubts that might come from him, and what he beautifies (for one) lustfully.
Striving against the infidels can be through the hand, wealth, tongue and heart. While striving against the sinners can be with the hand, tongue and heart as much as possible.
Jihâd is basically far'd kafaa'i (a communal obligation); when the requisite people carry it out, its obligation is removed from the rest. It will become meritorious in their own case.
Jihâd is among the best of supererogatory acts; its excellence is great. Texts of the Qur'ân and Sunnah exhorting to it are many. One of them is the Statement of Allâh the Majestic:
Verily, Allâh has purchased of the believers their lives and their properties; for the price that theirs shall be the Paradise. They fight in Allâh's Cause, so they kill (others) and are killed. It is a promise in truth which is binding on Him in the Taurât (Torah) and the Injeel (Gospel) and the Qur'ân. And who is truer to His Covenant than Allâh? Then rejoice in the bargain which you have concluded. That is the supreme success. [Taubah: 111].