Imamat of Imam Musa Kazim (as)

Hisham b. Salim, a Shi'ite master and notable, related about how he and his companions resorted to Imam Musa after the death of his father, saying:
I (i.e. Hisham b. Salim) and Muhammed b. Nu'man (known as) Sahib al-Taq were in Medina after the death of Imam Abu 'Abd Allah (al-Sadiq). The people had agreed that 'Abd Allah b. Ja'far was the leader of the affair (sahib al-amr) and the one who would undertake the office of the Imamate after his father. My companions I and came in to him. When we sat down, we asked him the following questions:
-How much poor-tax (zakat) should be paid on two hundred dirhams?
-Five dirhams.
-How much on a hundred dirhams?
-Two and a half dirhams.
They were astonished at this religious decision that has no relationship with the Islamic Law. That is because the minimum amount of dirhams is two hundred dirhams; and there is nothing on that which is less than it. Hisham sneered at this religious verdict that has no concept:
-By Allah, you are declaring the doctrine of the Murji'a.
-By Allah, I do not know the doctrine of the Murji'a.
Hisham and Muhammed left him while they could not see the way out of pain and sadness, for they did not come to know the Imam who would undertake the office of the Imamate after Abu 'Abd Allah (al-Sadiq). Then Hisham said: "(Shall I go) to the Murji'ites, the Qadarities, the Mu'tazilites, to the Zaydites, to the Kharijites?"
While Hisham and Muhammed were roaming in a current of suspicions and thoughts and were reflecting on a doctrine to follow, they saw an old man indicating with his hand to Hisham to follow him. Hisham thought that the old man was among the spies of al-Mansur and could understand their speech. He fearfully turned to his companion and ordered him to go away from him, that only he might be punished. He followed the old man, and he took him to Imam Musa b. Ja'far, peace be on him. When he came in to him, he became tranquil. When he sat down, the Imam turned to him and said to him with kindness and affection: "To me, not to the Murji'ites, nor to the Qadarities, nor to the Mu'tazilites, nor to the Zaydites...."
Hisham became happy, for he found his objective when the Imam told him about what he had in his inner self. This is one of the marks and signs of the Imamate. Then Hisham asked him the following question:
-May I be your ransom, has your father gone?
-Has he left through death?
-Whom shall we follow after him?
-If Allah wills, He will guide you to that man.
-May I be your ransom, your brother 'Abd Allah claims that he is the Imam after his father.
-'Abd Allah intends that Allah should not be worshipped (properly).
-Who is in charge of us after him.
He answered him with an answer similar to his first one, and Hisham asked him:
-Are you him?
-I am not saying that.
Hisham made a mistake in his speech, and he corrected his mistake, saying:
-Do you have an Imam over you?
He admired and magnified the Imam, to the extent that none knew except Allah. Then he said to him: May I be your ransom, may I question you like I used to question your father.
-Question. You will be informed but do not spread (the answer) around. For if you do spread it around, then slaughter will take place.
Then he asked him many questions, to the extent that he came to know that the Imam was a sea (of knowledge) which could not be exhausted out of his abundant knowledge and merit. After he had come to know him and been sure of his Imamate, he asked him:
-May I be your ransom, the Shi'a of your father is lost (without a leader). May I put this matter to them and summon them (to follow) you? For you have taken (a promise of secrecy from me).
-Tell those of them whose righteousness you are familiar with, but take (a promise of) secrecy from them. For if it gets spread around, there will be slaughter. And he pointed to his neck with his hand.
Then he went out while he was tranquil and happy-hearted due to what he had found. So his friend hurried to him and asked him:
-What happened to you?
Then he told him the story, and they both went to Zarara and Abu Basir. After they had met with them, they told them about the Imam's tradition. Thus, Zarara and Abu Basir hurried to the Imam and asked him some questions. He answered them, and they were sure of his Imamate. Then the Shi'ite masses went to the Imam in groups and pledged allegiance to him and acknowledged his Imamate. The overwhelming majority of the Shi'ites adopted his Imamate except the companions of Ammar al-Sabati, for they insisted on their own thoughts. ( Al-Mejalis, vol. 5, p. 328.)