I haven't seen this reported anywhere else, but Strategy Page claims:
Syria is apparently granting citizenship (and Syrian passports) to thousands of Iranian mercenaries like Hezbollah from Lebanon, some Iranians and Shia from other countries Iran recruited to fight in Syria. These newly created Syrians will be wearing Syrian Army uniforms as they take up position near the Israeli border. Israel suspected that Iran was planning this and now has to respond before these Iranian forces can carry out any attacks (as Iran has vowed to do) on Israel itself. Iran is desperate for a win because their recent efforts to hurt Israel have all been very embarrassing failures.
The report is part of a larger article on current developments in Syria.
If true, this is a potentially explosive development. Israel has long had a "line in the sand" policy that Iranian forces and their surrogates could not operate close to Israel's borders. Whenever that line was crossed, Israel struck back, hard. Now, it will become almost impossible for reconnaissance flights and/or satellite imagery to distinguish Iranians from Syrians, if both are wearing the same uniform and occupying the same camps. Israel can't afford that; so it's likely to start hitting at any major concentration of military forces in Syria that are within a hundred miles of its border. It can't afford to wait, only to find out the hard way that Iranian forces are launching an attack from a base that was left alone.
It's quite clear that Iran is seeking a confrontation with Israel at almost any cost - one where its forces' lack of technological sophistication can be offset by proximity. Your super-duper guided weapons and precision strike capability are great at a distance, but they count for a lot less if I can get within knife-fighting range of you before you deploy them. I suspect Iran would like nothing more.
This will bear watching, and in the short term, too. Israel has to respond to this. It has no real strategic or tactical alternative. That may, in turn, draw the USA into greater involvement in Syria - one that will entangle us even more than we already are. The New Yorker (admittedly not an objective source where the Trump administration is concerned) thinks that may already be happening. That's not a comfortable thought, to put it mildly.