An administrative court on Thursday ordered the auctioning of Al-Wefaq's assets to be held on October 26, the source said.
The group's dissolution in July drew strong criticism from UN chief Ban Ki-moon and Bahrain's allies in Washington and London, as well as Shia-dominated Iran which Manama accuses of meddling in its affairs.
After the latest court decision, security forces seized Al-Wefaq's assets including its headquarters outside Manama and two other offices in villages, the source said.
The accusations that led to the ban -- upheld by an appeals court last month -- included ‘harbouring terrorism’, inciting violence and encouraging demonstrations which threatened to spark sectarian strife in the country.
Al-Wefaq's leader, Sheikh Ali Salman, has been behind bars since December 2014 on charges of inciting hatred and calling for forceful regime change.
But on Monday Bahrain's cassation court overturned his nine-year jail sentence and ordered a retrial.
Al-Wefaq was the largest group in parliament before its lawmakers resigned en masse in protest at the crushing of Arab Spring-inspired demonstrations in 2011 calling for an elected government.
Political parties are banned in Bahrain, so Al-Wefaq operated as an association.
Also known as the Islamic National Accord Association, Al-Wefaq is heir to the Bahrain Freedom Movement which played a key role in protests in the 1990s that sought the restoration of the elected parliament scrapped in 1975.