"The doctor attending on Hazare has advised him two days of complete rest on medical grounds," Hazare's close aide Suresh Pathare said.
Hazare, who is currently in his native village, will leave for Delhi on December 10 and join the day-long agitation for a strong Lokpal Bill the next day, he said.
According to Pathare, the doctor has also prescribed some tablets for Hazare, "which are being sent to the village," he said.
Although, Pathare did not elaborate on the nature of Hazare's health problem, sources close to the activist said, he was suffering from severe back ache.
Hazare has already announced that he will sit on an indefinite fast in jail, if police do not give permission for his proposed protest at Delhi's Ramlila Maidan, later this month for a strong Lokpal.
Team Anna has sought permission from Delhi police for a fast by Hazare from December 27 at the Ramlila Maidan, if the Bill is not passed in the ongoing Parliament session.
Hazare had sat on a fast in Delhi's Tihar Jail in August, when the government did not give him permission to sit on a dharna in the national capital.