The requirement is to win a vote of confidence in the Knesset, not 61 votes in particular. According to Israel's basic law:
- (d) When a Government has been formed, it shall present itself to the
Knesset, shall announce the basic lines of its policy, its composition
and the distribution of functions among the Ministers, and shall ask
for an expression of confidence. The Government is constituted when
the Knesset has expressed confidence in it, and the Ministers shall
thereupon assume office.
Basic Laws of Israel: The Government
Because the Knesset is a 120-seat parliament, 61 votes is necessary to guarantee a majority. This figure was widely reported because a coalition of various small parties was required to form the government, and the parliamentary arithmetic in terms of member count was vital.
However, all that is required by law is a successful vote of confidence, which in this case was won 60-59 due to the abstention of one Knesset member. Unless otherwise stated, decisions in the Knesset are made by a majority of the members participating in voting:
- Save as otherwise provided by Law, the Knesset shall pass its decisions by a majority of those participating in the voting - those
abstaining not being reckoned as participating - and the voting
procedure shall be prescribed by the Rules.
Basic Laws of Israel: The Knesset
The government can be removed by a vote of no confidence, which does require an absolute majority of 61. These members also need to support the same alternative candidate, rather than just voting against the government.
(a) The Knesset may adopt an expression of no confidence in the Government.
(b) An expression of no confidence in the Government will be a
decision adopted by the majority of the Members of Knesset to request
that the President charge one of its members with the task of forming
(c) If the Knesset has expressed no confidence in the Government, the Government shall be deemed to have resigned on the day of the expression of no confidence. The President will, within two days, charge the Knesset Member named in the decision with the task of forming a Government.
This wasn't always the case - in 1990 the government led by Prime Minister Yitzhak Shamir was brought down by a vote of no confidence won 60-55, with 5 abstentions, but this vote took place under the old Basic Law in place from 1968 to 1992 which only called for an "expression of non-confidence", rather than a constructive vote of no confidence as in the current law.