3. IJMA'.--The third foundation of the Faith is called Ijma', a word signifying to be collected or assembled. Technically it means the unanimous consent of the leading theologians, or what in Christian theology would be called the "unanimous consent of the Fathers." Practically it is a collection of the opinions of the Companions, the Tabi'in and the Taba-i-Tabi'in. "The Law," says Ibn Khaldoun {17} "is grounded on the general accord of the Companions and their followers." The election of Abu Bakr to the Khalifate is called Ijma'-i-Ummat, the unanimous consent of the whole sect. The Companions of the Prophet had special knowledge of the various circumstances under which special revelations had been made; they alone knew which verses of the Quran abrogated others, and which verses were thus abrogated. The knowledge of these matters and many other details they handed on to their successors, the Tabi'in, who passed the information on to their followers, the Taba-i-Tabi'in. Some Muslims, the Wahhabis for example, accept only the Ijma' of the Companions; and by all sects that is placed in the first rank as regards authority; others accept that of the 'Fugitives' who dwelt at Madina; and there are some amongst the orthodox who allow, as a matter of theory, that Ijma' may be collected at any time, but that practically it is not done because there are now no Mujtahidin. The highest rank a Muslim Theologian could reach was that of a Mujtahid, or one who could make an Ijtihad, a word which, derived from the same root as Jihad (a Crescentade), means in its technical sense a logical deduction. It is defined as the "attaining to a certain degree of authority in searching into the principles of jurisprudence." The origin of Ijtihad was as follows:--Muhammad wished to send a man named Mu'az to Yaman to receive some money collected for alms, which he was then to distribute to the poor. On appointing him he said: "O Mu'az, by what rule will you act?" He replied, "by the Law of the Quran." "But if you find no direction therein?" "Then I will act according to the Sunnat of the Prophet." "But what if that fails?" "Then I will make an Ijtihad and act on that." The Prophet raised his hands and said, "Praise be to God who guides the messenger of His Prophet in what He pleases."[22] This is considered a proof of the authority of Ijtihad for the Prophet clearly sanctioned it. {18}