The 52-year-old woman was tied by her hands and ankles with gaffer tape by four men wearing balaclavas who entered her house uninvited in Nantes last Sunday, newspaper Le Parisien reports.
The woman was alone in the house while her husband went to the synagogue office for business.
“She was threatened with torture if she didn’t tell them where her jewellery was,” said a source close to the victim.
“The attackers explained they were waiting for ‘the rabbi’ to come back, talking about her husband – but her husband is not a rabbi.”
The four men eventually fled before the victim’s husband returned, but not before washing her arms and legs with detergent to erase any traces which could lead back to them.
Police guarded the victim’s home and the nearby synagogue that evening in case the attackers returned.