There are vast implications for any Israeli aggression in Syria, which may not be tolerated by Russia. It may place the US under Trump's leadership in a precarious position, not necessarily by its own initiative, discretion, design...
Figure. Syrian "Civil War" : Military situation in November 2017. Red: Syrian Arab Republic, Green: Syrian opposition, Yellow: Rojava (SDF), Grey: Islamic State of Iraq and the Levant, White: Tahrir al-Sham (formerly al-Nusra Front). The dispute, described here, pertains to the relatively short border between Israel and Syria (lower left). Source: Wikipedia.
Tel-Aviv, December 28 - following is the English translation of a short Hebrew Facebook post, "A Stern Warning", by Ran Edelist - a reputable Israeli journalist, specializing in military-intelligence matters. 
Figure. " A Stern Warning" - a short Facebook post on the evening of Thurdsday, December 28, 2017, by Ran Edelist, a reputable Israeli journalist, specializing in military-intelligence matters. Source: https://www.facebook.com/ran.edelist.3/posts/171558366928534
A Stern Warning
Right now, a dispute is underway between IDF's leadership and the Prime Minister and his Minister of Defense.  The dispute pertains to the nature of response to the advancement of Syrian government forces, backed by Russian air force and Hezbollah, towards the Israeli-Syrian-Jordanian border point in the south of the Golan heights, the slopes of Mount Hermon in the northern Golan heights, and the vicinity of Al-Quneitra.
The advancement of Syrian government forces is aimed at annihilating the rebels, who operate under Saudi/US patronage with limited IDF support.
Netanyahu claims that the situation amounts to Iranian penetration and threatens an Israeli response. In parallel, he is making representations that there is "strategic understanding" between Israel and the US regarding such circumstances - of Iranian approach to the Israeli-Syrian border. 
Ehud Barak spoke a week ago about the potential of a patently illegal order, which IDF must disobey.  An order to interfere in the war in Syria might be legal/democratic,  but lacks any tactical or strategic logic, and would cost human lives in vain. Therefore, it should be deemed patently illegal. 
We are forewarned!
Edelist's warning should be assessed on the background of extremely unusual conditions in Israeli internal politics, where "winds of a revolution" have been noticed by various high-level figures, and top deep-state figures are openly involved in the growing massive demonstrations against Netanyahu. 
In particular, Edelist's warning should be assessed on the background of the extremely unusual statement made by former Israeli PM/former IDF Chief of Staff Ehud Barak last week, that circumstances were nearing, where the IDF/Shin-Bet leadership might have to disobey Netanyahu and stage a rebellion. The statement gained additional weight when it was later disclosed that Barak had held a private meeting with current IDF Chief of Staff Gadi Eisenkot 24 hours earlier.
"Strategic understanding" in this context is likely to be a reference to some unknown, possibly also non-existent US-Israeli understanding in conjunction with the November 10, 2017, Russian-US-Jordanian Memorandum of Principles, which was announced by both the US and Russia.  The Memorandum ignored Israel and its demands relative to the outcome of the Syrian "civil war". In particular, it allowed Iranian forces to gain access to areas that are as close as 5 km from the Israeli border.
Israel immediately expressed its opposition to the Memorandum, and claimed to be at liberty to act in Syria as it deemed fit. 
Additionally, it later became clear that there was a wide difference between the US and Russia relative to interpretation of the Memorandum: The US claimed that it meant that Iranian forces would have to leave Syria. Russia claimed that Iranian and Russian forces were invited by the sovereign government of Syria, while US presence in Syria was patently illegal and must come to an end.  In response, the US refused to withdraw its forces from Syria and announced that they would stay there for the foreseeable future. Putin made a short surprise visit to Syria and announced withdrawal of Russian forces. However, Russian air and naval bases in Syria are a permanent feature. 
In this context, it should also be noted that Netanyahu has recently made the full Israeli government delegate its authority to declare war to the smaller "Security Cabinet".  The legality of such decision is dubious.
It should also be noted that the situation is almost a repeat of a 2010 confrontation between Netanyahu and the security apparatus, relative to attacking Iran. 
The entire situation should be also assessed on the background of the pending (mid-January?) police recommendation to indict Netanyahu in at least some of the corruption investigations that engulf him. In such context, it has been clear for months that there is concern that Netanyahu would try to divert public attention by initiating a security crisis, or even a war. Various parties have claimed that under the circumstance he has "no mandate" to make such critical security decisions.
Obviously, there are vast implications for any such aggression by Israel in Syria, which may not be tolerated by Russia, and which may place the US under Trump's leadership in a precarious position, not necessarily by its own initiative, discretion, design...