the inhabitants of the district upon which the enemy has descended and taken up positions rise to drive him back; once they have done so, the obligation is lifted from everyone else. Even if the enemy merely approaches the Abode of Islam without actually entering it, the people are still required to go out and confront him.
The second category of obligatory jihad is that the ruler (imām) must send a detachment against the enemy at least once each year. He should either accompany them himself or dispatch someone he trusts, so that they may invite the foe to Islam, encourage them, restrain their aggression, cleanse Allah’s religion of their defilement, and fight them until they embrace Islam or pay the jizyah. If the jizyah is offered, he accepts it; if they refuse, he fights them. The people, with their wealth and their persons, are also obliged to take part in that expedition until it is known that those who have set out are sufficient to confront and contain the enemy. When that requirement is satisfied, the duty falls from the rest, while those who have gone forth enjoy a mighty reward over those who remained behind; they are not required to march out all together.
The supererogatory form of jihad consists of sending out group after group, dispatching raiding parties whenever the Muslims are strong and an opportunity arises, and lying in wait for the enemy by maintaining frontier garrisons (ribāṭ) in places of danger.
The ascetic al-ʿUmari—ʿAbd Allāh ibn ʿAbd al-ʿAzīz ibn ʿAbd Allāh ibn ʿUmar ibn al-Khattāb (may Allah be pleased with him)—asked Mālik ibn Anas: “Abu ʿAbd Allāh, is it permissible for us to refrain from fighting those who abandon the rulings of Allah and judge by something else?” Mālik replied, “That depends on whether the Muslims are many or few.”
Abū ʿUmar said: Although Mālik’s answer was given in connection with fighting people other than idolaters, it nevertheless includes the idolaters as well and embraces the duty of commanding right and forbidding wrong. It is as though he were saying: “Whoever knows that, were he to challenge the enemy in single combat, they would kill him and he would inflict no harm upon them, may withdraw and join another group of Muslims. He is not permitted to give up his life to someone he cannot overcome, from whom he cannot escape, and from whose death the Muslims would gain nothing.” In my view, Mālik’s statement resembles what Sufyān ibn ʿUyaynah narrated from Abū Najīḥ, from ʿAṭāʾ, from Ibn ʿAbbās