Such a move is expected to ensure that should Gantz be given a mandate to form a government by President Reuven Rivlin after Netanyahu fails to do so, he will be unable to form a sustainable coalition.
The commitment states that under no circumstances would the factions currently allied to Netanyahu join a minority coalition led by Gantz.
The factions also committed to work tirelessly to bring about the dissolution of such a minority government and vote against any of its legislation.
"We commit to only join a coalition led by Prime Minister Netanyahu that will include the signatories of this commitment: Shas, United Torah Judaism, Jewish Home and Tkuma – either as part of a unity government or a Likud-led narrow coalition," the document reads.
New Right leaders Naftali Bennett and Ayelet Shaked refused to sign the document, claiming their commitment to Netanyahu's bloc was firm and did not need to be put down on paper.
Netanyahu has approximately one week left of the four-week period granted to him by Rivlin to form a government.
The president can extend this period by another two weeks if he chooses or he can simply ask another lawmaker to try to put together a coalition.
Neither the Netanyahu nor Gantz in the center-left have enough support to form a right-wing or center-left government, respectively.
Netanyahu's failure to do so after the April national elections led his Likud party to dissolve the newly elected parliament and hold an unprecedented second round of voting in six months, which took place on Sept. 17.
The prime minister has been accused of planning to hold a third round of elections rather than allow Gantz the mandate to form a coalition.