An unclassified report of the French DGSE (the equivalent of CIA) dated April 2002 deals with Hamas creation.
Israelians encouraged Hamas as a religious opponent to PLO (« les Israéliens encouragent le Hamas en tant que pendant religieux de
l’OLP ») that they wanted to weaken (« affaiblir »).
The strategy consisted in inciting to an armed conflict (« inciter au conflit armé ») between the 2 organisations and create a civilian Palestinian war (« créer ainsi une guerre civile palestinienne »).
Israel then erroneously thought that with Hamas, Palestinians
will be busy fighiting each other instead of struggling against
Israel (« commet l’erreur de croire qu’avec le Hamas, les
Palestiniens seraient occupés à se battre entre eux au lieu de lutter
contre Israël »).
For more information , refer to this French article Pourquoi Israël a aidé le Hamas à se développer
In this Source:Mossad's secret wars by Yvonnick DENOEL, it is written that:
According to an Israelian source, (this) support to Islamist was conceived by a former Mossad member and encouraged by the (Israelian) military government of Gaza, that authorized massive funds transfer from Saudi Arabia since they benefit to Islamists and not PLO.
However, there is no clear evidence of the involvement of Shin Bet in an active support to Hamas, such as funding, training or weapon deliveries.
In a book written by Shimon Perez, Boutros Boutros-Ghali and André Versaille, titled "60 ans de conflit israélo-arabe: témoignages pour l'histoire" (60 years of Israeli-arabian conflict: testimonies for history), Boutros-Ghali, a former UN Secretary-general, said in a diplomatic way:

What can be translated to:
Boutros Boutros-Ghali: Personally, I am not sufficiently informed to know whether Israelians had encouraged Hamas and Jihad to weaken PLO, even if it seems to make sense.