hearts were united." What afterwards proved the main source of revenue in Islamic states dates from the taking of Khaibar; for the rent paid to the state by tolerated communities for the right to work their land developed long after Mahomet's time into a poll-tax for Unbelievers (see CALIPHATE, e.g. B. § 8 and MAHOMMEDAN INSTITUTIONS), and a land-tax for all owners of land. Immediately after the taking of Khaibar certain communities, of which the most notable was Fadak, sent tribute before they had been attacked and reduced; their land was regarded by Mahomet as his private domain, but after his death it was withdrawn from his heirs by his successor Abu Bekr, in virtue of a maxim that Prophets left no inheritance, which in the opinion of Fatima was contrary to Koranic doctrine, and invented by Ayesha's father expressly for the purpose of excluding her and her husband from their rights; and this is likely to have been the case. As a military organizer Mahomet, as has been seen, was anxious to adopt the most advanced of contemporary methods, and more than once is said to have scandalized the Arabs by foreign innovations, as at a later time the Moslem chiefs who first used gunpowder scandalized their co-religionists. The unit in his armies seems to have been, as of old, the tribe, under its natural leader; that he introduced no more scientific division, and nothing like a hierarchy of officers was perhaps due to the difficulty of reconciling such a system with the equality of all Moslems. As has been seen, the Koran only assumed the character of a civil code as the need for one arose; and for some time after Mahomet's arrival at Medina old-fashioned methods of settling disputes continued in use, and doubtless in accordance with precedent where such was known. For difficult cases, even in Arab opinion, divine inspiration was required; and since Mahomet naturally claimed to be in sole enjoyment of this, his utterances soon became the unique source of law, though he did not at first think of organizing a code. Such a plan is said to have occurred to him, and he even wished to dictate a code upon his deathbed; but his friends supposed or professed to suppose him to be delirious. A table regulating the "Alms" was left by him, it is said, in the possession of Abu Bekr; but other traditions assign another origin to this document. Just as there were no regular officials for the arrangement of business, so there were none for its execution; when punishment was to be administered, any follower of Mahomet might be called upon to administer it. In the case of the massacre of the Banu Quraizah care was taken to see that some of the heads were struck off by their former allies, in order that the latter might be unable at any time to bring a demand for vengeance. The Prophet hoped by the mere terror of his name to make complete security reign throughout Arabia, and there is no evidence that any system of policing either it or even Medina occurred to him.