The Israeli commission investigating the massacre of Palestinian refugees in Beirut completed the process of gathering evidence today by accepting Defense Minister Ariel Sharon's written answers to two questions.

Sharon had been called for cross-examination by lawyers for Maj. Gen. Yehoshua Saguy, the chief of Army intelligence, who agreed to drop their request that the defense minister appear in person before the inquiry board.

Sharon and Saguy are among nine senior Israeli officials, who also include Prime Minister Menachem Begin, Foreign Minister Yitzhak Shamir and Army Chief of Staff Lt. Gen. Rafael Eitan, who have been warned by the commission that they may be harmed by the investigation's findings. A spokesman for the panel said the commission has set Jan. 16 as the day for final arguments before it by lawyers for the nine officials.

Israeli sources have predicted that it will take a month to six weeks after all the arguments have been heard for the inquiry board to issue its final report, which is expected to set off a major political debate.

The panel devoted last week to hearing new evidence from six of the nine officials, some of whom asked to cross-examine other witnesses in the case. Although the commission said it would attempt to conduct as much of the week's proceedings as possible in public, virtually all of the testimony was heard behind closed doors.