Ibrahim Zakzaky, leader of the Islamic Movement of Nigeria (IMN), was arrested in 2015 under a crackdown on followers in the northern city of Zaria.
Rights groups say troops killed some 350 of his supporters and buried them in mass graves.
The IMN has staged repeated rallies demanding Zakzaky's release, leading to violence that has left dozens dead.
The government announced on Sunday it was banning the group after at least eight people were killed in the latest clashes with security forces.
State prosecutor Dari Bayero, speaking to reporters after a hearing in the northern town of Kaduna, said Zakzaky's doctors had applied for him to be flown to India to receive intensive treatment for an undisclosed ailment.
He said the prosecution had urged the court to reject the request.
"The court is going to rule on Monday (August 5) on whether to allow him to go or enjoy the medical facilities (available) in this country," he said.
Defence lawyer Femi Falana said Zakzaky's health and that of his wife, who is also detained, had deteriorated so much that they were unable to attend the hearing.
"Their health condition is so bad that they could not come," he said.
The government has repeatedly ignored previous court rulings for Zakzaky's release on health grounds, insisting he was being held in the national interest.
IMN spokesman Ibrahim Musa said the group was "not happy" with the postponement decision and that almost daily demonstrations would continue.
"The protests will continue because we cannot fold our arms and see our sheikh dying," he said.
Zakzaky and the IMN have been at loggerheads with the government for years because of his call for an Iranian-style Islamic revolution in Nigeria. Northern Nigeria is predominantly Sunni Muslim.
