The preliminary passage of legislation aiming to bar Israelis who visit "enemy states" from serving in parliament has sparked heated exchanges.
Leading Israeli-Arab MK Azmi Bishara has been accused of spying
Israeli-Arab MPs said the plan showed the Knesset was "racist" and vowed not to abide by any eventual law.
One of the sponsors defended the proposal, reportedly saying: "Enough of Arab Knesset members spitting in our faces and us saying it's raining."
In April an MP who had visited Syria and Lebanon was accused of spying.
Azmi Bishara fled Israel after facing charges of spying for the Lebanese group Hezbollah during last year's war.
He says he is the victim of persecution.
Fears of spying
The legislation passed by 52-19 votes on Tuesday will have to be approved another three times before being enacted.
It seeks to make it illegal for Israelis who visit "enemy states" - including Syria, with whom Israel remains technically at war - without permission to serve as a Knesset member.
The proposals were put forward by two right-wing members - Zevulun Orlev and Esterina Tartman.
"Visiting enemy states stirs fear that sensitive security information could be relayed," the Jerusalem Post quoted Mr Orlev as saying.
"The Bishara episode and the incitement used by some of the Arab MPs, such as their trips to Syria and meetings with Hamas leaders, are not in the realm of free speech, but form clear encouragement of armed attacks and terrorist activities against Israel."
Ms Tartman reportedly said it was "time for Israel to open its eyes. Enough of Arab Knesset members spitting in our faces and us saying it's raining."
The move was bitterly rejected by Israeli-Arab MPs.
"The Knesset is steeped in racism," said Ahmed Tibi of the United Arab List party.
"Corrupt members of the Knesset want a Knesset without Arabs... If I am invited [to an enemy state] I will go despite the law."
"If we have to choose between loyalty to our people, or serving the Knesset, then good luck to the Knesset," said Muhammad Barakei, who heads the Hadash party.
"All the racists can choke."