Ya'qúb b. Isḥáq al-Kindí,*

though he was a Jew, was the philosopher of his age and the wisest man of his time, and stood high in the service of al-Ma'mún. One day he came in before al-Ma'mún, and sat down above one of the Imáms of Islám. Said this man, “Thou art of a subject race;*

why, then, dost thou sit above the Imáms of Islám?” “Because,” said Ya'qúb, “I know what thou knowest, while thou knowest not what I know.”

Now this person knew of his skill in Astrology, but had no knowledge of his other attainments in science. “I will write down,” said he, “something on a piece of paper, and if thou canst divine what I have written, I will admit your claim.” Then they laid a wager, on the part of this person a cloak, and on the part of Ya'qúb a mule and its trappings, worth a thousand dínárs, which was standing at the door. Then the former asked for an inkstand and paper, wrote something on a piece of paper, placed it under the Caliph's quilt, and cried, “Out with it!” Ya'qúb b. Isḥáq asked for a tray of earth, rose up, took the altitude, ascertained the ascendant, drew an astrological table on the tray of earth, determined the positions of the stars, fixed the signs of the Zodiac, worked out the subjective conditions and affinities,*

and said, “On that paper he has written something which was first a plant and then an animal” Al-Ma'mún put his hand under the quilt and drew forth the paper, on which was written “The Rod of Moses.” Al-Ma'mún was filled with wonder and expressed his astonishment. Then Ya'qúb took the cloak of his adversary, and cut it in two before al-Ma'mún, saying, “I will make in into two …”*

This matter became generally known in Baghdad, whence it spread to 'Iráq and throughout Khurásán, and was widely discussed. A certain doctor of Balkh, prompted by that fanatical zeal which characterizes the learned, obtained a book on Astrology and placed a knife in the middle of it, intending to go to Baghdad, attend the lectures of Ya'qúb b. Isḥáq al-Kindí, make a beginning in Astrology, and, when he should find a suitable opportunity, suddenly kill him. Stage by stage he advanced, until he went in to the hot bath and came out, arrayed himself in clean clothes, and, placing this book in his sleeve, set out for Ya'qúb's house.

When he reached the gate of the house, he saw standing there many handsomely-caparisoned horses belonging to descendants of the Prophet*

and other eminent and noble persons of Baghdad. Having made enquiries, he went in, entered the circle in front of Ya'qúb, greeted him, and said, “I desire to study somewhat of the science of the stars with our Master.” “Thou hast come from the East to slay me on a pretence of studying Astrology,” replied Ya'qúb, “but thou wilt repent of thine intention, study the stars, and attain perfection in that science, and wilt become one of the greatest Astrologers in the Church of Muḥammad (on whom be God's Blessing and Peace).” All the great men there assembled were astonished; and Abú Ma'shar*

con­fessed and produced the knife from the middle of the book, broke it, and cast it away. Then he bent his knees and studied for fifteen years, until he reached that eminence which he reached in Astrology.