Book of Jihād
Legal ruling
It is a communal obligation (farḍ kifāyah).
When a sufficient number have undertaken it, it becomes a recommended act.
It is not individually binding except on a free1, adult, sane, healthy Muslim male who has enough wealth to provide for himself and for his dependants during his absence, and who can secure provisions and a mount for a journey long enough to permit shortening the prayer.
It is recommended2 to accompany the warrior when he departs, but not to go out to welcome him on his return.
The most meritorious voluntary deed is jihād, and naval expeditions are superior to all others.
Martyrdom expiates every sin except outstanding debt.
A debtor who lacks the means to repay may not volunteer without his creditor’s permission, nor may anyone volunteer without the consent of either free, Muslim parent.
Ribāṭ is likewise recommended: remaining stationed at the frontier for the sake of jihād. Its minimum duration is one hour, its full term forty days, and it is better than residing in Mecca3. The best ribāṭ is at the point of greatest danger.
Muslims are not permitted to flee from an enemy force whose numbers do not exceed twice their own, even if this means one man facing two. If the enemy outnumbers them by more than two to one, retreat is permitted.