As for the fact that this obligation is confined to free men, I know of no dissent concerning it. Moreover, the vast majority of jurists agree that a further condition is the permission of one’s parents—unless the obligation has become an individual duty, such that no one can fulfil it unless everyone goes forth.
The foundation for this ruling is the sound report that a man once said to the Messenger of Allah—may Allah bless him and grant him peace: “I wish to take part in jihad.” He asked, “Are your parents alive?” The man replied, “Yes.” The Prophet said, “Then strive on their behalf.”
They differed, however, regarding the permission of parents who are idolaters, and likewise over whether the creditor’s leave is required when a person is in debt. This last difference rests on the Prophet’s words—may Allah bless him and grant him peace—when a man asked him:
“Will Allah expiate my sins if I die steadfast, seeking His reward in His path?”
He answered, “Yes—except for debt; Gabriel has just informed me of this.”
Nevertheless, the majority allow a debtor to go forth, especially when arrangements exist for the settlement of his debt.
Chapter Two: Identifying Those Who May Be Fought
As for those who may be fought, the scholars are unanimous that they are all the polytheists, in light of the Almighty’s words:
“Fight them until there is no more persecution and religion is wholly for Allah” (al-Anfāl 8:39).
An exception is reported from Mālik, who said that it is neither permissible to initiate hostilities against the Abyssinians nor simply to abandon them, citing the Prophet’s statement—may Allah bless him and grant him peace: “Leave the Abyssinians so long as they leave you.” When Mālik was asked about the authenticity of this report, he did not affirm it but remarked, “People have always refrained from attacking them.”
Chapter Three: The Forms of Harm Permissible Against the Enemy
As for the harm (nikāyah) that may be inflicted on the enemy, it falls under three headings: property, lives, and persons—that is, enslavement and possession.
Regarding the harm that consists of enslavement, it is, by consensus, permissible with respect to every category of polytheists—male and female, elderly and young, minor and adult—except for monks. Some scholars held that monks should be left alone, neither killed nor enslaved, in view of the Prophet’s words—may Allah bless him and grant him peace: “Leave them and that to which they have devoted themselves,” and following the practice of Abū Bakr.
Most scholars maintain that the ruler has discretion regarding prisoners of war and may choose any of the following: grant them their freedom, enslave them, execute them, accept ransom, or impose the jizyah. A group, however, held that it is not permissible to execute a captive.