40-18 Al-Hakim Abu Ali Al-Husayn ibn Ahmad al-Bayhaqi narrated that Muhammad ibn Yahya al-Sowli quoted on the authority of Ubaydillah ibn Abdullah ibn Tahir, “Al-Fadhl ibn Sahl advised Al-Ma’mun to seek nearness to God the Honorable the Exalted and His Prophet (S) by visiting the relations of kin, pledging allegiance to Ali ibn Musa Ar-Ridha’ and returning to them the rule which Ar-Rashid had taken away from them. This was not possible to do. Therefore, from Khorasan Al-Ma’mun sent Abi ad-Dhahhaq and Yasir - the servant to bring Muhammad ibn Ja’far ibn Muhammad (one of Imam As-Sadiq’s offspring) and Ali ibn Musa ibn Ja’far to him. This happened in the year 200 A.H. (815 A.D.). When they brought Ali ibn Musa to Al-Ma’mun in Marv, he appointed Ali ibn Musa as the successor to the throne after himself. He also ordered that the troops be granted one full year’s salary. He declared this issue to all Muslim lands. He called him Ar-Ridha’ and had silver coins coined in Ar-Ridha’’s name. He ordered the people to put aside their black clothing that was a sign of the Abbasids, and asked them all to wear green clothing. Then he married off his daughter Umm Habib to Ar-Ridha’ , and married off his other daughter Ummul Fadhl to Ar-Ridha’’s son, Muhammad ibn Ali . He himself married Pooran - the daughter of Al-Hassan ibn al-Sahl. This was because of her uncle Fadhl and all of this happened in one day. However, Al-Ma’mun did not really like that the Caliphate (the rule) be turned over to Ar-Ridha’ after him.Al-Sowli added, “What Ubaydillah ibn Abdullah narrated for me was correct from several points of view. Oun ibn Muhammad narrated on the authority of Al-Fadhl ibn Abi Sahl Al-Nowbakhti - or from his brother - that when Al-Ma’mun decided to establish Ar-Ridha’ as the successor to the throne, I told myself, ‘By God, I will test Al-Ma’mun to see if he sincerely wants to do this or not.’ Then I wrote a letter as follows and handed it to his servant who was the one who reported Al-Ma’mun’s secrets to me in writing, “Thul-Riasatayn has decided to draw up the contract for succession to the throne. The horoscope is in position of Cancer, the fourth sign of the Zodiac (the fourth month). Jupiter and Cancer are in it. Even though Jupiter is in the upright position it is a month of turmoil. Whatever contract is established in that month will have no good ending. Additionally, Mars is in Libra. That is in the seventh house which indicates that any contracts established in it are unfortunate. I am reporting this to the Commander of the Faithful so thatyou do not blame me for not doing so, if anyone else reports it to you.’ Al-Ma’mun replied, ‘Return this letter by the same messenger who delivered it to you as soon as you read its contents. Take care that no one finds out about what you wrote to me, since that might result in Thul-Riasatayn changing his mind. Beware that if anyone finds out, I will consider you to be blameworthy for negligence.’ As soon as I read the reply, the world became too small for me and I wished that I had never written him that letter. However, Thul-Riasatayn Al-Fadhl ibn Sahl himself feared this bad horoscope and changed his mind since he had sufficient knowledge of astrology. However, I swear by God that I feared for my life. I rode towards where he was and asked him, ‘Do you know of any star in the sky that is more prosperous than Jupiter?’ He said, ‘No?’ I asked, ‘Do you know of any stars in the sky that are more prosperous than Jupiter in the upright position?’ He said, ‘No.’ Then I said, ‘Then do not change your mind about drawing up the contract for the succession to the throne. Do not change your mind while the sky star of prosperity being Jupiter is in its most prosperous position being the upright position.’ Thul-Riasatayn then decided to continue on with what he had decided to do, and drew up the contract. However, I feared Al-Ma’mun and did not know whether I would be dead or alive until the succession to the throne took place.”