Imam Kazim (as) - Martydom

When the Imām was in a critical condition and was about to meet the decreed end, he summoned al-Musayyab b. Zahra and said to him: “I have told you about (my) departure to Allah, the Great and Almighty. When I ask you to give a drink of water and you see that I relax, and that my face turns yellow, red, green, and changes colors, tell the tyrant (Hārūn al-Rashid) about my death.”
Al-Musayyab said: “I went on watching him until he, peace be on him, asked me to give him a drink of water and he drank it. Then he summoned me and said: ‘O Musayyab, this dirty one (i.e. al-Sindi b. Shāhik) will claim that he will undertaking washing and burying me. Far be it from him! Far be it from him! When I am carried to the cemetery known as the cemetery of Quraysh, bury me in it, do not raise my grave higher than four separated fingers, and do not take anything of my earth to get the blessing of it, for each earth of us is forbidden except that of my grandfather al-Husayn b. ‘Ali, for Allah, the Great and Almighty, has made it cure for our Shi‘ites and friends.”
Al-Musayyab said: “Then I saw a person like him sitting beside him. I recognized my master al-Ridā, peace be on him, when he was a boy, so I wanted to ask the person, but my master Mūsā shouted at me and said: ‘Didn’t I prevent you (from doing such a deed)?’ Then the person disappeared. I came to the Imām and found him a motionless body. He passed away, so I told (Hārūn) al-Rashid about (his death) ( Hayāt al-Imām Mūsā Bin Ja'far, vol. 2, pp. 514-515 )

Reference :The life of Imām'Ali Bin Mūsā al-Ridā