Google this very term.
Okay, so I did:
http://freedom-articles.toolsforfreedom.com/top-10-proofs-isis-us-israeli-creation/
None of this is plausible. Do you have other conspiracy theories that Israel is behind?
“Israel is backing ISIS?”
Israel is engaged in realpolitik with regards to Syria.
Fundamentally they view Assad as a greater long term threat than ISIS and Al-Qaeda. Assad is a Shiite and on friendly terms with the Shia in Lebanon (Hezbollah) and Iran (Republican Guards etc.). Israel considers Iran their number 1 threat at present. Therefore, Israel sees Assad as a greater threat than ISIS. That is why they bomb Assad and treat injured Free Syrian Army (Sunni Jihadis) forces in their hospitals.
http://www.timesofisrael.com/the-curious-case-of-israels-syrian-patients/