Residents of capital Manama attended a demonstration on Thursday night to renew their allegiance to the popular cleric who has been allowed to leave the country to receive medical treatment, Bahraini sources reported.
Demonstrators also voiced solidarity with the political activists imprisoned by the Al Khalifa ruling regime.
After more than 400 days of house arrest in Diraz, a town west of Manama, Sheikh Qassim was given the permission to leave for London on July 9 with a temporary passport after his health deteriorated.
Sheikh Isa, in his late 70s, was stripped of his Bahraini nationality in 2016 on charges of "serving foreign interests".
Bahrain, a close ally of the US in the Persian Gulf region, has been witnessing almost daily protests against the ruling Al Khalifa dynasty since early 2011, with Manama using heavy-handed measures in an attempt to crush the demonstrations.
Scores of Bahrainis have been killed and hundreds of others injured and arrested in the ongoing crackdown on the peaceful demonstrations.