Parliamentary discussion of a bill to advance national elections to replace Prime Minister Memachem Begin's government were postponed today in the wake of the assassination last night of Sheik Hamad Abu Rabia, the only Bedouin member of Israel's parliament.

Deffering to the funeral of Abu Rabia, who was shot to death while sitting in his car near a West Jerusalem hotel, members of Begin's Cabinet canceled meetings with their respective politcal factions to work out a motion to disolve the Knesset, or parliament, and hold elections in June, five months before Begin's four-year term is due to expire.

Sources in the ruling Likud coalition and the opposition Labor Party alignment said the motion may be put off several days until factions can agree on when the elections will be held.

Begin, meanwhile, assumed the position of acting finance minister, replacing Yigael Hurvitz, who resigned Sunday in a Cabinet dispute over Israel's economy. Hurvitz took with him the three members of the Rafi faction, triggering a coalition crisis and agreement by a majority of Cabinet ministers to put the government to a test of new elections.

Israel police arrested six suspects in connection with the murder of Abu Rabia, 51, who had been the most outspoken advocate of Bedouin rights. Four of the suspects are Israeli Druze Arabs from the western Galilee town of Yarka, near the home of Druze Sheik Jaber Muadi, who was supposed to have shared a Knesset seat with Rabia under a rotating agreement. sHowever, Rabia refused to relinquish his seat in parliament and recently had said that there had been threats to his life.

Abu Rabia was the first member of Israel's Knesset to be assassinated since the founding of the state nearly 33 years ago.

More than 10,000 Bedouins attended his funeral near the Negev town of Arad and he was eulogized by Israeli leaders in statements issued in Jerusalem.

Begin called Abu Rabia "a good man and a loyal citizen of Israel." Former foreign minister Abba Eban said the victim was "a warm colleague who defended the Arab interests which he was a custodian. He had a policy of peace within Israel and between Israel and its Arab neighbors."

Israeli President Yitzhak Navon called on all Bedouins in Israel and the occupied territories to exercise restraint while police conduct an investigation into the murder.

The religious affairs minister has said he does not mind losing his immunity because he wants to stand trial and prove the charges are "a political libel." But his lawyers were reported seeking a delay until after the Israel elections.