Imam Musa (as) guides Ali Ibn Yaqteen

Imam Musa, peace be on him, took great care of ‘Ali b. Yaqteen; he had fear for him of the authority of Harun al-Rashid, for the affair of his becoming a Shi‘ite was not hidden from the followers and hirelings who sought nearness to the authority through every horrible means. The Imam came to know that such hirelings would not leave ‘Ali unless they put an end to him. So the Imam, peace be on him, undertook guiding him and raising danger from him. That was through two things:
Firstly, the Jubbah
Al-Rashid gave some excellent clothes to ‘Ali b. Yaqteen as gift; among them was an excellent, black jubbah brocaded with gold the caliphs worn. When it reached him, he immediately sent it to Imam, peace be on him, as a gift. The Imam returned it to him and wrote to him: “Keep it and do not take it out from you; you will face an affair and you will need it for the affair. When the jubbah a long with the Imam’s letter reached ‘Ali b. Yaqteen, he read the letter and kept the jubbah. He put it into a basket and set a seal on it. A period of time elapsed, ‘Ali b. Yaqteen changed his policy toward one of his boys who had knowledge of his affairs, and he immediately went to Harun and said to him: “Surely ‘Ali b. Yaqteen believe in the Imamate of Musa al-Kazim; every year he sends him the alms of his possessions, gifts, and valuable things; this year he has sent him the whole of that along with the black jubbah which you gave to him as a gift at the time so-and-so.”
The condition of al-Rashid changed when he heard of that as if that a sword hit him on the face. He angrily said: “I will discover that. If the affair is just as you have said, I will kill him. That will be as part of the punishment for him.”
Then he sent a messenger for ‘Ali b. Yaqteen. When he stood before him, he turned to him and asked him: “What about the black jubbah I gave to you as gift and singled you with it from among the rest of my special group?”
Ibn Yaqteen turned to him calmly and said to:
-It is with me, Commander of the faithful! It has been perfumed and put into a basket on which a seal has been set!
-Fetch it now!
-Yes, I hear and obey!
‘Ali summoned a servant of his and told him about where the jubbah was. He gave him the keys, and he quickly went. Shortly after that he brought the jubbah and put it before Harun. He ordered the seal and the basket to be opened. The jubbah was folded; it was as it had been before; and nothing hit it, so the anger of al-Rashid calmed, and his revolution abated; and he said to ‘Ali: “Return it to its place. Take it and go away with safety. After this we will believe no informer against you!”
Then he ordered a prize to be given to him and ordered the ignoble informer to be flogged a thousand times. He was flogged five hundred times, and he perished. As for ‘Ali b. Yaqteen, he peacefully went out; Allah saved him from the punishment and tyranny of Harun. A poet has composed a poem on this miracle, saying:
The pure one (Imam Musa) returned the clothes to Ibn Yaqteen and said to him: Take them, for you will be questioned about them. Without doubt your enemy will be a loser! ( Nur al-Abbsar, p. 136. Al-Manaqib, vol. 2, p. 356. Bahr al-Anwar. )



Reference : THE LIFE OF IMAM MUSA BIN JA'FAR AL-KAZIM