Al-Husayn ibn Sa’id narrated from Ibn Abi Umayr, from some of his companions, from Abu Abdullah عليه السلام, who said:
Imam عليه السلام said: "The one afflicted with smallpox (majdoor) and the one with fractures (kaseer) should perform tayammum if they become junub (ritually impure)."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 195