Indeed he took that action as political necessity for he did...

Indeed he took that action as political necessity for he did not want to alienate his Persian friends and supporters. For not only prominent friends of Ahlul Bayt were appointed to responsible positions, but particular public favor was shown to the family of the deceased Imam ‘Ali Al-Ridha’ (as).

One of the Imam’s brothers was chosen to preside at the annual pilgrimage in Makka, and it was but a short time until Mamun married his own daughter Umme Fadhl to Imam Muhammad Taqi (as) According to Yakubi, Mamun bestowed upon the bride groom one hundred thousand Dirhams, and said, “Surely I would like to be a grandfather in the line of the Apostle of God and of ‘Ali Ibn Abi Talib (as).

It is a well-known fact that the Imam gave all this money to the poor rather than spend it upon himself, which his wife Umme Fadhl, who was the daughter of Mamun did not like at all and complained to her father about this. But Mamun knew the ways of Ahlul Bayt, rejected her complaints and told her to live like the wife of an Imam of the Ahlul Bayt of the Prophet. The story of Mamun’s first meeting with the young son of Imam ‘Ali Al-Ridha’ (as) is interesting.

One day, when the young Imam was only nine years old, the caliph Mamun went out hunting. The Imam was standing silently by the road side where some children were playing. The caliphs entourage came that way. Seeing the soldiers of the caliph all the children ran away, but the young Imam remained standing at his place.

Noting this, Mamun stopped his carriage and asked, “Young man, why did you not run away like the other children?” The Imam replied calmly, “Neither had I committed a crime, nor was I blocking the way. Why should I have run away or be afraid? And I also know that you will not cause any unnecessary trouble when your way is not blocked." Mamun was surprised with this mature reply and asked, “What is your name?” “Muhammad,” came the reply. Whose son are you? asked Mamun.

"Son of ‘Ali ibn Musa (as) ." Mamun rode on. During his hunt the hawk returned to him with a fish in its beak. Mamun was surprised. He returned back toward the city. Once again, he found children playing on the same spot, who ran away seeing the caliph’s soldiers, except this young man who said he was Muhammad son of ‘Ali ibn Musa (as) who remained where he was.

Mamun hid the fish in his palm, stopped his carriage near the Imam and said, “Tell me, what is there in my fist?” The Imam replied, “God created clouds between earth and sky.