Ali ibn al-Hasan, from Muhammad ibn Ali, from al-Hasan ibn Mahbub, from Umar ibn Yazid, from Abu Abdillah عليه السلام, peace be upon him: Imam عليه السلام said: “When the servant observes seclusion for worship (itikaf), let him fast.” And Imam عليه السلام said: “There is no seclusion for worship (itikaf) less than three days, and stipulate a condition upon your Lord عز وجل in your seclusion for worship (itikaf) just as you stipulate a condition in your state of consecration (ihram). That is in your seclusion for worship (itikaf) in the case of an occurrence, if there occurs to you an illness that descends upon you from the command of Allah سبحانه وتعالى.”